As a followup, we have canceled our subscription to Soylent 2.0 ("regular" flavor). My partner has now had 6 bottles of the stuff at different times of day, with and without taking beano first. In almost all cases, there was extremely painful gas/bloating. Strangely once without beano, there was no issue at all. But every other time it was there. Without beano it was debilitating and onset within minutes. With beano it was just extremely uncomfortable and onset within 30 minutes. I suppose we could have experimented with a significant increase in the beano dosage, but having to take it every single time goes against the primary reason for consuming Soylent in the first place, so that's not an acceptable solution.
For reasons I can't explain, both Cacao and Coffiest flavors have no issues at all. No beano required, they're just fine. Also for equally unknown reasons, even Soylent 1.3 gives her problems sometimes, though quite infrequently and exclusively at night (post 7PM). Go figure. It's infrequent enough that she's still willing to drink 1.3, but just makes sure to have gas pills handy at night.
This is a definite bummer as we were really optimistic when Cacao and Coffiest were both acceptably digestible, but such is life. Fingers crossed for a near-future version that better addresses her problems with "plain" 2.0...
Oh side note, when she reacts badly to 2.0, it's very much how she reacts sometimes when consuming popcorn (or anything corn-based), as she generally needs to take beano or other digestive enzymes before consuming corn. And 2.0 smells/tastes like popcorn too... coincidence?