Simplest answer (other than obviously Ep 4 was written decades before Eps 1-3):
He lied.
He doesn’t know the circumstances of Luke’s appearance at his doorstep (as it were), and his job - his ONLY job - is to keep Luke safe. Until he sees the message, he doesn’t know WTF is going on. Why would he admit owning a droid? He’s supposed to be just some old geezer in the desert.
Simplest answer (other than obviously Ep 4 was written decades before Eps 1-3):
He lied.
He doesn’t know the circumstances of Luke’s appearance at his doorstep (as it were), and his job - his ONLY job - is to keep Luke safe. Until he sees the message, he doesn’t know WTF is going on. Why would he admit owning a droid? He’s supposed to be just some old geezer in the desert.
Or the classic: “it was a military issued droid, it was never his”
Yeah. The droid belonged to the Jedi Order.