That is my understanding. That said, as my EASA licence contains a specific rating validity dated, which is based upon my biennial - I don't think I'd like to try arguing that it was valid if that date had been passed. It seems a dangerous place to start playing "barrack-room lawyer".
Incidentally, whilst it's still nominally biennial, the FAA have decided to stop calling it a "Biennial flight review", and it's now just a "Flight Review" on the grounds that there may be reasons to have them at different intervals depending upon currency need.
G