Most journals certainly have a separate Methods section where they describe the entire protocol. I believe this paper has the same section too. Can you be more specific what you think authors missed out in description of the methods?

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.