First off, Wow! Thanks so much for all this great feedback.
It's going to take me a bit to digest all these replies and respond.
I will say that I have to disagree with the one suggestion/assertion that fills only occur when choosing a green part marker.
I have written 15 or so songs in BIAB and found I get drum fills (as long as I allow them by right clicking the part marker) with either Blue-A or Green-B, but I agree that the change/fill is more pronounced when it's before a Green-B part marker, but still there for the Blue-A part.
On this song I get them on either type of part marker, just not all of them, and when I re-generate and play, some appear where there were none, and others that were there before disappear.
One new question: can a drum fill (which is supposed to be in the bar before the part marker) show up as JUST a single cymbal crash on the first beat of the bar with the part marker?? If so, then it is working, but certainly not what I'd call a fill/pick-up setting up the next bar.

Before addressing some of the other thoughts, suggestions and questions, let me give you some information on the song I'm working on with the issue:
Style: CTRWZPS.STY Slow Country Waltz with Pedal Steel. It's in 3/4 time, and although the style tempo is 85, I upped it to 114 for my tune.
Is that a possible problem?
The RealDrums used are NashClassicWaltzSW^

If anyone is interested, I'd be happy to send you the .SGU file.

Again, many thanks to all who responded. I will reply in greater detail tomorrow, as well as report on my further experimenting. (Yes, I do keep looking for other ways to work around as I am still pretty much a novice)
Thanks again!

2023 BIAB Ultrapak, Reaper, EZDrummer 2 & 3, Roland VS-2480, Tascam 38 Reel to Reel 8-Track