I do recall this issue from 5-6 months ago but I think it was fixed by adding leaf decay attribute to crop leaves. I tested it by cutting down an apple tree, one crop leaf block decayed while the other is still hanging there after a few minutes.

It uses random ticks, similar to crops so could just be unlucky? I didn't want to add unnecessary blockstates so it checks directly around it for leaves, and if there are any attached, it won't start to decay until they do.

Well, as you can see from the picture, all the leaves decayed (I have an instant leaf decay mod) so you could immediately see the crop leaf block hanging there, not decaying after many minutes.

in 1.17 they'll act more like vanilla leaves, there is no persistence, however, once they're 7 distance away from the log they can decay.