byis to always put the timestamp in the filename (or metadata, though messing with .mkv/mp4 metadata intentionally is currently beyond me), because tooling can and will destroy create/modify times. my h265 conversion batch file (growing more complicated, more on that in a sec) just annihilates them. or transferring to windows in the first place does, I forget. I think I complained about this already but: hey it's still happening.
despite doing a lot of things at once (because that process works for me), I am leaving some things until later. "can I pull original creation times out of metadata somehow and use that to provide obvious FS level timestamps" is one of those things.