Note that the VIC-20 and C-64 and older Commodore machines indeed displayed it as back-arrow:
https://en.wikipedia.org/wiki/PETSCII PETSCII has only uppercase letters in its powerup state, an up-arrow ( ↑ ) instead of a caret ( ^ ) in position $5E and a left-arrow ( ← ) instead of an underscore ( _ ) in position $5F, these two variants are common in ASCII-1963. So basically this comes from the ASCII-1963 usage.
