As an author, I'd like to write my protocol Methods in the past tense
It saves rework if the the protocol Introduction and Methods are written as if they are the final review's Introduction and Methods. That idea is re-enforced by using the past tense, and avoids the tedious changes of tense for the review.
John Hilton commented
Maybe an alternate solution is to write the majority of methods for both protocols and reviews in a tense-neutral way, using fragments or lists rather than narrative sentences. May have advantages for linked data if could be done consistently with controlled vocab.