Well you know, I just programmed a 3/4 beat on my drum machine, just 3 different bass hits, 1 2 3, and gave it some practice. I think I can explain better about not fitting. Anyways, usually in my head playing a 6/8 rhythm, I'm instinctively counting 1 & A, 2 & A, etc or singing the rhythm with that kind of feel, you know the four subdivisions of 3....but when you do that the count of 2 falls
after the bass's 2, so I guess it feels off, even though the notes are played in cadence, it's the feel caused by my internal clock. However, just now during practice with the drum machine, I played the same 6/8 rhythm, but counted 1&2&3&, then of course the count coincided with the notes of the bass. Same rhythm, same cadence, but a different feel created by my internal counting.
I guess it's the application of counting. Sure the bass is playing two measure of 3 as a way of playing 6/8, but he's counting in his head 1,2,3 (probably?). So say I count a 6/8 in my head like I would normally 1&A2&A, my count is either right on top, his 123 is my 1&a, or I play 1&A2&A in one measure of his 123 count, so that his 2 falls on my (1)A, which in a folkloric context that kind of cross rhythm feels natural, but in jazz feels off, at least to me. The bass seems to be marking out the secondary pulse of a 6/8 with his 3/4 bass line, and I need to count that way too to feel on. If I count the primary pulse, I feel off.
Seems like I read something about this phenomenon of 2 divisions of three vs. 3 divisions of 2 in a book recently.