I tried it just now, and I did manage to jam exactly 125 g into the larger container. It was a heck of a tight fit though and I did need to spend a minute or two trying to jam it in there.
Interestingly, I only managed to fit 90 g into the smaller of the two containers this time around whereas last time I fitted 100 g into it. I guess I just got lucky last time and it all fell into place, or my last batch of Huel was more dense (unlikely). At any rate, don’t rely on easily being able to fit 100 g into that smaller container.