Well I've been plugging away at it enough, and I have at least now hit the MINI progressive on Battle of Bastogne at 3Dice (for the second time). Alas I also seem to have discovered a 'tell', this happened the first time I won the MINI and I put it down to random chance, but it's now happened again so I think it's definitely a thing.
Look at my autoplayer as the scatters drop in, 104 games remaining, the feature is set to FULL AUTO mode (so it does all the shooting and stuff all by itself), the only thing it stops on is 50x or better AFTER the feature plays out.
So what happens normally is the feature kicks off all by itself, the autoplayer does its thing, and if the pay is less than 50x it just carries on, if it's more than 50x it stops after the feature finishes, as per my configuration of the autoplayer.
The difference here is that it stopped BEFORE the feature started.
So basically it stopped on this screen here, and it wouldn't carry on until I manually clicked on the 'YEAH' button, already I'm thinking, 'Hang on, last time this happened I won the MINI'.
It then shows me the controls screen, again, you never see this when it's in full auto mode. (Because why do you need to, you've told the feature to play itself.)
I can still manually press the 'AUTO-AIM' button to get the feature to play itself, which it does, but now every vehicle it's aiming at has the little crosshair over it, the only time I've seen this before is when I last won the MINI.
So here's the tank, this is rare-ish on a three scatters trigger (I reckon about 1 in 6 or so), but I was already expecting a tank to show up, and honestly, I was expecting it to be a progressive.
And yep, there it is, the MINI progressive.
Round total including the MINI was 435x stake, I'm not complaining about the win (obviously I'd have preferred the MEGA!), but it does look like you can tell in advance if your bonus round will yield a progressive on this game, because that's the second time the bonus round has played out like that now, and it never does that for a normal bonus round, irrespective of whether or not it hits the 50x stop trigger.
Now it's possible 3Dice have done this deliberately because they don't want you to miss a progressive bonus round in case you're out of the room whilst the autoplayer just does the whole thing all by itself, but personally I'd rather not know upfront whether or not a tank kill would yield a progressive.