Interesting recommendation, I haven't heard of them. I checked out their MTB shorts, and this model[0] is basically identical to a pair I've bought on Amazon from various "Chinese" retailers of different names (like ARSUXEO), which gives me pause due to the massive inconsistency in quality from pair to pair.
Do you know if Decathlon actually takes an active role in the production, or are they just buying bulk e.g. from Alibaba? Their website doesn't really say much and what they do say just feels kind of generic.
[0] https://www.decathlon.com/products/mountain-bike-shorts-900-...