HR & Calorie Burn

I'm probably not going to ask this correctly, probably use the wrong terms and not really make sense - but "I" know what I mean ...
Anyway, I use a HRM for my calorie burn, my GPS watch doesn't calculate, so I go to a website and put my age, weight, avg HR, and time into the calculator, and I get an estimated calorie burn. I used a different website than usual, which led to my questions.

First, let me say - that I'm fit already, don't really "worry" about calories burned, eating back calories, eating extra for workouts, I'm not asking for THAT purpose, and frankly, would rather avoid any "debate" as far as logging the calories. I log purely for the purpose of tracking my workouts. I don't care if I burn 2 or 2000, it's more just a tracking mechanism for me.

That said - I put in my Strength Training last week into the new website calculator - it was 109 for 90 minutes of avg heart rate. And the website told me that for anything less than 115, it would not calculate and said it's below 65% of my maximum heart rate. Which I get.

So, now to my question, IS there really no calorie burn if I'm below 65% of my maximum HR? My resting HR is about 42, my maximum on calculators is about 180. So... no one specific.... just as example, people putting in housecleaning or sex as exercising, would it really be exercise, or calculated if it's below a certain % of maximum HR.

Again, so I do yoga...90 minutes, I log it, clearly, it's extremely below my 65% maximum HR - but it's still exercise I log, just not count calories. I'm tempted to just start putting in 1 calorie burned for these exercises into MFP. But really, is exercise really not exercise if not sustained for any amount of time over 65% MHR?

Like I said, I understand my question, but am sure I'm explaining it horribly wrong.