Theoretically it IS possible, and there are working, practical, proof-of-concept research on the subject.
A couple of examples:
Learning to Extract Flawless Slow Motion from Blurry Videos
Blurry Video Frame Interpolation
The picture below is from the second paper.
However, as of this writing, I couldn't find any feasible-to-use, (commercial or otherwise) ...
The solution at question " Lower framerate without re-encode " looks promising:
ffmpeg -discard nokey -i input.mp4 -c copy -vsync 0 I-only.mp4
By manpage there should be 5 levels of frame discarding: none, noref, bidir, nokey, all.
I tested this with older ffmpeg 4.2.4 and h265 and it had no effect. Probably not implemented yet.
The solution was to delete the presets I was using in both Premiere and Media Encoder and start from scratch. Somehow these 2 had gotten out of sync and the presets in PrPro and Media Encoder we're not using the same frame rate. I didn't understand how this got out of sync unfortunately.