Literate native speaker--polyglot journalist difference, in my humble opinion. And BAFTA can put things any way they like when their turn comes. No, the difference is semantic, not stylistic.
***** NOT A TEACHER *****
(1) You always ask the most interesting questions.
(2) I checked "Professor Google," and it seems that
the preposition for is favored. Of course, I did not
check all the results, but I found only one use of as --
in the Reuters article.
(3) I most respectfully suggest that you use for.
(4) By the way, many results avoided the as/for problem
by simply phrasing the information in another manner.
(a) Here is how the Los Angeles Times (Hollywood is a part
of the City of Los Angeles) put it:
Natalie Portman ... won the lead actress Academy Award.