Joe,
A lot of it is that as you say, you sew slowly. I find that the most trouble seems to occur for me when I get moving fast.
Not all threads seem to care, but definitely, as the thread has time to start to snap back and forth and "load up" a lot of energy - that's when the take off problems occur. And yes, I've had spools actually launch - that really messes up tension!!
Even Superior threads says it's the last 5% of the equation that you can affect. It's not the first go to for tension problems. I do find though that a stack wound spool never climbs up and down the spool pin regardless of me sewing at mach speed or not, and the bouncing of a cross wound spool will correspond to the up or down part of the wind on the cross wound thread.
The extra twist that's being introduced has the potential to be very bothersome with some threads.
All I'm really trying to do usually is let people know that adding weight to a spool that already doesn't want to be turning, or using a cross wound spool on a vertical spool pin, may be OK for -some- applications, but it's possible that that one spool you're going to try one day is really going to object and all hades is going to break loose - and it won't be because your machine hates the thread, it'll be because the rules were tighter for that thread and they were "broken".