Writing style when discussing other people's research in discussion/introduction
Neither alternative is good or bad.
I would put the citation first if the author or the history is important:

Darwin [On the Origin of Species, 1859] argued that natural selection ...

but the citation last if you just want to tell your reader where they can look to check your facts:

Darwin's finches continue to evolve [J. Wiener, The Beak of the Finch,
1995 (reprint)].

So it's a case by case choice. In this case I think your advisor is right.