This is the stated motivation, although I must confess I have no idea how the A-theory is supposed to be even a partial explanation of becoming.

I don't think it's supposed to be an explanation of becoming, I think it's supposed to be a model of time that takes becoming into account. Explanations have to ground out somewhere.

I actually think the presentism/eternalism distinction is more likely susceptible to shminux's charge of vacuity than the A-theory/B-theory distinction.

The opinion has born put forward a number of times, but I am still waiting for someone to substantiate it by putting forward an explanation of how change is equivalent to stasis.

I can see how "time is passing through me" is equivalent to "I am passing through time" ....but those are two dynamic theories.