I'm afraid I won't be of much help: the sources I know about (and you surely know them too) are forum's wiki and usage examples in available code (TelloLib, pytello, TelloPy).
I have not analyzed video stream from Tello (I'm by no means a programmer); for what I understand about h.264 stream is that PPS and SPS formats are quite well defined, but their presence in stream is optional; they can be provided out of band or even be left out completely, when sender and receiver have some pre-agreement about parameters used.
For what I read in pytello and TelloPy, SPS/PPS are sent in reply to command 0x0025 (wiki lists it as "start video", but apparently there is no problem in sending it repeatedly), so maybe they're sent on demand only and absent otherwise? But this is only my speculation -- you have at least three developers here that have managed to receive and decode video, so better ask them

aTello app is even opensource, but unfortunately it has some glitches in video decoding; author of TelloFPV claims best video results (and these claims are not unfounded, video is really smooth), but no sources to read I know of.