why eat less than a surplus on "rest days"

No need to eat excess calories if no workout/exercise is involved. The longer the weight gain, the less fat you will gain. 1-2lbs per month is more realistic for leaner gains.

Forever bulking crew here so I'm bulking at a slow pace.

I eat the same amount of calories daily while bulking because my calorie intake is specifically designed for everyday eating. I believe some ppl do it to minimize fat gain, but in my mind i think that the body needs energy/calories to repair as the muscle repair takes approx 36 - 48 hours i believe, so i always want to be at surplus, although it might not be necassary.

I eat 2000 kcal and I burn on average 800 kcal a day. Why complecate things?

Like the others have said I think it is to do with minimizing fat gain. Probably wont make a big difference but I do not think they realize that muscle protein synthesis stays elevated for up to 36 hours after a work out. They are limiting calories during the peak of the growing window.

http://www.ncbi.nlm.nih.gov/pubmed/8563679

The time course for elevated muscle protein synthesis following heavy resistance exercise.
MacDougall JD, Gibala MJ, Tarnopolsky MA, MacDonald JR, Interisano SA, Yarasheski KE.
Source
Department of Kinesiology, McMaster University, Hamilton, Ontario.
Abstract
It has been shown that muscle protein synthetic rate (MPS) is elevated in humans by 50% at 4 hrs following a bout of heavy resistance training, and by 109% at 24 hrs following training. This study further examined the time course for elevated muscle protein synthesis by examining its rate at 36 hrs following a training session. Six healthy young men performed 12 sets of 6- to 12-RM elbow flexion exercises with one arm while the opposite arm served as a control. MPS was calculated from the in vivo rate of incorporation of L-[1,2-13C2] leucine into biceps brachii of both arms using the primed constant infusion technique over 11 hrs. At an average time of 36 hrs postexercise, MPS in the exercised arm had returned to within 14% of the control arm value, the difference being nonsignificant. It is concluded that following a bout of heavy resistance training, MPS increases rapidly, is more than double at 24 hrs, and thereafter declines rapidly so that at 36 hrs it has almost returned to baseline.

I usually eat the same amount of calories everyday, regardless if it's a rest day or not. I'm of the opinion that my body needs calories on rest days to recover from the previous day's workout. Sometimes on weekends I'll double up on workouts in which case I'll try to eat a little more. I have a heck of a time putting on weight, so this has worked for me so far.

I'll just fix the problem by never having rest days! Lol cardio EVERY DAY!

And to the guy saying it makes you laugh that people are afraid to gain weight? Seriously? Why are you on my fitness pal then?

You don't have to eat a different amount each day-- remember your body needs rest and calories on off days to grow.

I find it easier to just eat the same amount every day.

It's about the total calories over time. It is, and always has been (whether losing weight, maintaining, or gaining), about calories in vs. calories out.

And to the guy saying it makes you laugh that people are afraid to gain weight? Seriously? Why are you on my fitness pal then? JERK.

Because this is in the section for people who want to gain muscle weight. And that means a certain amount of fat gain along with the muscle. And that means you just have to make peace with it and not be afraid to put on a bit of chub if you want the muscle.

People are often so afraid of putting on a bit of fat that they never really end up putting on any muscle either. Which is the thrust of the thread.

To answer the OP. I'm not sure if it's bollocks or not. But proponents of this style of eating say it improves your p-ratio.

There's obviously leangains (although I think you're meant to just eat maintenance on your non-lifting days if you're bulking on it). And LM's UD2.0 has a variant where you do all the crazy depletion stuff earlier in the week at a slight deficit and then do the power/strength stuff later in the week at a massive surplus/carb up.

Anecdotal reports from users of both have stayed lean while adding mass. But then you've got to ask: would they have stayed lean just eating a mild surplus and doing the same thing? They may have been genetically gifted, young, male, lean: basically, all the things that lend themselves to a favourable p-ratio. And with no counter-class, who can say?

It may even be behavioural, in that the discipline necessary to keep the cycling going, stops you going too far into fulking territory, which is easy to slip into when you're bulking (finally, I can eat all the foods, etc)

This is for fat loss, considering you don't lift weights 6 days/week. It's all about carb cycling, protein stays the same. Why would you want to eat so many carbs on non-workout days? Doesn't make sense as this will lead to added body fat. If you are meeting protein macros on rest days then you are still giving your body the nutrients to repair. Protein builds muscle, carbs don't.