I suppose I am not sure entirely what constitutes an emulator and what doesn’t, but I always thought an emulator mimics (emulates) a certain systems architecture, i.e. has to be slower by design than the real thing. In wine, however, windows system calls are replaced / re-routed to the underlying linux system calls which are often much faster, which is why wine often exceeds windows in performance executing windows binaries (assuming you can get them to run at all :)

WINE has a FAQ on the matter - https://wiki.winehq.org/FAQ#Is_Wine_an_emulator.3F_There_seems_to_be_disagreement

Short story, it depends what you use WINE for and the perspective you're looking from. I think from a binary's POV that thinks it is calling Windows OS it is emulation.