NTSC requires specific counter formats because -- at least -- there are two different "stories" the counter tells you. One "story" being the How Many Frames Are There in the video you are looking at (before the play-head). Another -- What Is The Number of the given exact frame in the video in Accordance With The NTSC Regulations. (Everybody knows there goes 'Frame #1002' after the 'Frame #1000' in NTSC.) (Hence the "Non-Drop Frame" & "Drop Frame" counter modes.)
...But... When it comes to ...errr... "full frame"-per-second formats, what goals can not be achieved without the things going beyond the "Hr.:Min.:Sec.:Fr.#" & "pure Time". Including WHATEVER 50 or 100 or 120 or 1256 fps. It seems to be beyond my clear understanding at the present moment.