If it did, that would not be a big deal since the Protoevangelium is not canonical, and the timing of the wedding is not a dogma of the Church.
Then how is someone to know which parts of the Protoevangelium are true, and which parts are not true?
But there is no contradiction: the Protoevangelium does not describe the wedding at all, it merely mentions that the priest did not know of the wedding at the time Mary was noticeably pregnant.
The contradiction was in the stated plan that the marriage take place so as to ensure that no one would suspect illicit activity of the part of Joseph. The Protoevangelium clearly does address that with the opposite result. Joseph was forced to give an accounting after an accusation.
To say, "I am a virgin" indeed does not stress any intention about the future, but to say "I know not man and therefore cannot become pregnant in the future, contrary to your prediction" very much stresses the intention, and the latter is what Luke effectively saying in 1:34.
The KJV says "Then said Mary unto the angel, How shall this be, seeing I know not a man?". That is a huge difference. The NAB says "But Mary said to the angel, "How can this be, since I have no relations with a man?". It's the same thing. Mary was making no such pronouncement about her future intentions, she simply proffered her (then) chastity.
Like with any historical evidence, you compare elements of it with what else you know. What, exactly, does strike you as inaccurate in the Protoevangelium and why?
contradiction was in the stated plan that the marriage take place so as to ensure that no one would suspect illicit activity of the part of Joseph
The homilist thinks that the Holy Spirit arranged the events so that Christ is perceived as a legitimate son of Joseph, and we know that he was. At the same time, Annas the scribe did accuse Joseph and Mary of having sexual relations. The resolution is in chapter 16:
And the priest took the water, and gave Joseph to drink and sent him away to the hill-country; and he returned unhurt. And he gave to Mary also to drink, and sent her away to the hill-country; and she returned unhurt. And all the people wondered that sin did not appear in them. And the priest said: If the Lord God has not made manifest your sins, neither do I judge you. And he sent them away. And Joseph took Mary, and went away to his own house, rejoicing and glorifying the God of Israel.
Annas suspected a defilement and tried both by ordeal. In the end he was satisfied that the relationship was somehow proper. He probably assumed that Jesus was Joseph's biological son and that it was good in the eye of God despite her earlier commitment to chastity, which saved the reputaton of the Holy Family, just as the homilist suggests.
Greek has no undefinite article. It has a definite article, absent in this case: "epei andra ou ginosko". Your case would be served if Luke wrote "epei ton andra ou ginosko" -- I do not know the man, which would indicate absence of premarital relation specifically with the betrothed bridegroom. Both indefinite article employed by King James and the absence of the article employed by Douay can connote either virginality at the present or virginality forever. But her future intention to remain virgin is seen not from this phrasing in itself but from her not assuming that the prophesied son will be hers and Joseph's.