Seems you are right.
This is also exactly the "main" line given by Adrien Demuth "The Modernized Reti" where he doesn't seem happy with the possible alternative 2.g3 Bb7 3.Bg2 g6!? and he therefore also prefers Owen's Defense. In his book he assesses the line after 4.d4 as "enough for an opening advantage" for White. When looking up I was surprised that 2...c5 would also be a possilbe transposition to a Sicilian sideline - although unlikely to be played according to Demuth.
I know there are a lot of people who like Owen's Defense, and let's agree to disagree on this one
However, my question is this: I don't see any way for white to exploit the move order of 1.Nf3 b6, without allowing black a transposition to a mainstream opening. 1.Nf3 b6 2.e4 looked most promising at first, but then 2...Bb7 3.Nc3 e6 4.d4 leads to a line which AFAIK is considered to be equal and gives black good play. Does anyone have any good suggestions against this move order, or do I just have to accept that 1.Nf3 b6 is as good as any other move?