To be fair, that wasn’t a PT thing, that was an ROTJ thing. Look what Anakin’s spirit is wearing on Endor.
Back in '83 I assumed Anakin was appearing in Tatooine garb as a kind of symbolic ‘return to innocence’ type thing. In the original novels Anakin had been a farmer like Owen, so it made sense that he would appear in his old duds at the Ewok party. The idea that these robes were official Jedi threads is/was absurd.
When you see all three of those Jedi, and they’re all wearing basically the same thing, the implication there is clear.
Also, “original novels”?
Sorry - novelizations (or novelisations). In the SW novelization Obi Wan tells Luke that Owen had wanted Anakin (not named at this point) to stay on Tatooine and concentrate on his farming. The film itself implied that Obi Wan had recruited Luke’s father for an ‘idealistic crusade’ despite Owen thinking he should have “stayed here and not gotten involved”. So this suggested (to me) that Anakin had been a farmer. Since Anakin was in Tatooine garb at the end of ROTJ, and Lucas himself made it plain that Luke had been in Jedi-garb in ROTJ (which wasn’t tan desert-robes), I naturally assumed that ghost-Anakin was in his old desert apparel.
The idea that Obi Wan was in fact sporting official Jedi-wear (whilst in hiding mind you!) that just so happened to be identical to Tatooine desert-wear is ridiculous.