The devs in the comments of that video do have some valid complaints about the added complexity of not being able to use the standard Java filesystem APIs anymore with the new permissions model, but still, it has been 6 years.
I interpreted that statement as "this is available in API level 19 and up", not "this was introduced on the same date that we originally released API level 19", but it looks like you're correct: https://www.youtube.com/watch?v=zxHVeXbK1P4 That's way older than I was expecting.
If you need to do stuff like recursively enumerate files in a shared directory, it's slow without workarounds to avoid the extra IPC calls. For stuff like syncing the shared directory in the background, the performance impact is not material (20-30ms per file).
The devs in the comments of that video do have some valid complaints about the added complexity of not being able to use the standard Java filesystem APIs anymore with the new permissions model, but still, it has been 6 years.