My headcanon for Owen not remembering 3-PO is that
- The odds are so astronomical that 3-PO would show up at his doorstep 20 years later in a Jawa sandcrawler that he doesn’t even consider that it could be a droid he once owned
- most protocol droids sound similar (TC-14 sounds prissy too).
- 3-PO is a different color to when he owned him
- He doesn’t even have the droid for any period of time before he before dies (as in, maybe he would have remembered eventually).
Point 1 is the big one though.
Not for anything, but 3PO also never tells Owen his name, and is in a completely different state of repair compared to the protocol droid he had over 20 years ago. The more worthwhile argument to have is why Obi-Wan doesn’t recognize R2, or why R2 doesn’t recognize Yoda or Dagobah after it’s been established (in the canon Clone Wars show) that they travelled there together.
There’s nothing to indicate Obi-Wan not remembering R2.
I got no answer for the Yoda thing though.
TCW plays fast and loose with continuity in general. I still think Ahsoka doesn’t really gel with ROTS.
EDIT: I saw your edit but i’ll just leave this here in case people want to jump in.