-
I've not seen it on any other MTB trousers, but I've not been looking. 🤷
I think the half length fly zip reduces bunching. Does mean you need to pull the waistband down a bit if you want to pee.
Two sets of poppers on the main body of the trousers, plus one set on the flap that covers the fly. This allows for a bit of adjustment.
The fabric is stretchy too. I wouldn't say they have masses of adjustment, but they're not fixed when it comes to waist tension.
These are fine:
https://www.decathlon.co.uk/p/men-s-water-repellent-mountain-bike-cycling-trousers/_/R-p-309674