Eh, suggestions from more senior people are in practice instructions. The risk in ignoring them is that something comes back to bite you and you look like an idiot for not following the suggestion of the senior.
Not necessarily. It depends on culture (local or otherwise). A senior needs to carefully instill an understanding of when a suggestion is optional; for some seniors, this may be "never". I personally prefer when direct instructions are mandatory but anything framed as a suggestion allows personal discretion (and requires willingness to defend having not followed the suggestion).