I know what you mean, but the title of this thread is about "Flight Reviews and BFRs. not an IPC.
I know what you mean, but since we're talking about flight reviews, we should be looking at 61.56
61.56 covers your IPC, and specifically states,
"(c) Except as provided in paragraphs (d), (e), and (g) of this section, no person may act as pilot in command of an aircraft unless, since the beginning of the 24th calendar month before the month in which that pilot acts as pilot in command, that person has—"
"(d) A person who has, within the period specified in paragraph (c) of this section, passed any of the following need not accomplish the flight review required by this section:"
"(1) A pilot proficiency check or practical test conducted by an examiner, an approved pilot check airman, or a U.S. Armed Force, for a pilot certificate, rating, or operating privilege."
So this can happen at any time as long as it has happened within the last 24 calendar months prior to acting as PIC. If you need it for an IPC, then you must do it every 6 months. But as I said, we're talking about Flight Reviews not an IPC.
That would be a different thread called Instrument Proficiency Checks.