The Protoevangelium is evidence that temple virgins were married to custodial marriages so that they not defile the Temple at puberty. This is the only point here. The Church does not teach thaqt definitively, but the doctors of the Church did notice that Luke 1:34 does not quite compute without some similar state of mind at the time of annunciation.
If you want to argue that Luke 1:34 does not definitely proove her perpetual virginity, I agree, -- but it points to it. That was Forest Keeper's question, and I answered it.
And we vehemenently disagree that Luke strongly points towards Mary ever being a "temple virgin."
Also, the Protoevangelium does not prove custodial marriages either considering that someone made the entire book up. It can not be trusted a source for anything.