I'm using Premiere to caption several 23.976 fps timelines. Our client is uploading the video and captions to YouTube, and says "the timings are not set properly". I haven't uploaded captions to YouTube, but I went to the YouTube Studio page, clicked on "Subtitles", and dragged in a caption file. The timecode of the first caption says, 01:00:06,144 --> 01:00:07,395, but it should be 01:00:02:13 - 01:00:03:19. Obviously, this difference is fairly significant.
When I reimport the exported SRT back into Premiere, the timecodes are correct. However, the frame rate of the SRT file is 30.00 fps. I just saw on an older post that the frame rate shouldn't matter.
The post you linked to was talking about framerate on import. Trent was pointing out that PR 2021 no longer "assigns" a framerate to the caption track/caption stream. But (I think incorrectly) shows a framerate of 30fps. PR is actually matching the caption stream to the sequence it is in. It is not actually a "30 fps" file.
And if you think about, a .srt caption file has nothing in it that tells you what framerate it "is." The timecodes simply have to fit the video (and therefore the video rate). What you describe sounds like Youtube is interpreting the caption file and changing the timecode?
I have learned a lot about captions, but caption framerate and how it is handled by different platforms has eluded me. I have seen posts about captions being out of sync with various framerates and platforms for years.
I'm leaving town and may not be able to test this. I'd export the beginning of the video (a few minutes), burn in the captions, and burn in the timecode. Export srt for that test segment. Then upload and see what Youtube is doing with it.