Unfortunately, PlayTo/JumpTo/ScrubTo were not meant to be user-facing and the function names turned out to be misleading. We tried to describe in them in the documentation as “low-level calls”, but there’s still confusion with that.
For the next release (4.26), we have renamed those functions to SetPlaybackPosition and the time format (frames, seconds, marked frame) playback state (playto, jumpto, scrubto) are now arguments. They’re still meant to be low-level calls, but we’ve also provided a new function, “PlayTo”, which is probably what you want. If you’re building from source and can grab a changelist, I can provide you with the changelist that has this new functionality.
For now, you’ll need to wrap your own “player” but figuring out the frame of the marked frame you want to play to, call play, and stop when the playback position hits or goes beyond that frame.
Sorry for the confusion.