I can imagine that for the sake of being concise (big Journals have text limits), they might have moved details to Supplementary sections.
Another reason one might find methods to be incomplete is when they refer to a previous paper and build on top of that, which is not entirely a bad strategy because this allows readers to go back to previous method in its original version than reading a duplicate version in new paper.
See https://www.protocols.io/view/human-colon-tissue-clearing-an... and compare to the amount of detail even in the supplemental methods.
Again, I think the concision and “refer to previous methods” approach is mostly* fine for discovery papers, but if the method is the thing, I want all the gory details in one place.
* but also, academics hate chasing down chains of references, some of which are in journals their university doesn’t subscribe to.