Well, in the EU, navigational droids like R2 do go through a factory reset on a regular basis, to avoid glitchy behavior. Doesn't seems unrealistic to me, from a CS point of view, when neural networks are involved. Luke never did it for Artoo because he liked it this way, but mechanics have trouble servicing the droid and the XWing.
I don't think that's the reset that doesn't make sense.
Even more so when an infant Leia has no reason to want its personality preserved, and a Bail Organa that has ALL the reasons to think a reset is the best way to protect Leia, even if the reset wasn't standard practice.
It's the whole idea that they had to link Artoo and Threepio with Anakin to begin with. Especially Threepio, I'd say.