Yes it is. Except that, apparently unbeknownst to thee, Mt 1:20 and Luk 2:21 use different words translated in English as one word "conceive."
The Church has always taught that the Word became incarnate, by taking the flesh of Mary in her womb, and became Man (i.e. took on a human nature). There was no "seed" and no "conception" by "seed."
The way you read things suggests some sort of divine-human sexual event.
Nope. A few things.
1. Conceived is the appropriate translation. Matthew, in particular, is relating to the Isaiah 7:14 prophecy that says a virgin will conceive. If conceive is not permitted to mean "become pregnant" in that verse, then virgin is not permitted to mean "sexually inexperienced female." In that case, we have no virgin and no pregnancy.
2. Since it is the Holy Spirit who is the active agent in the pregnancy of Mary, there is never the hint of sexual relations. "Come upon" and "overshadow" are clear indications that something special is taking place in this instance. In other biblical cases, one reads about "lying with" and "knowing."
Therefore, Mary clearly became pregnant. That had an inception point caused by the Holy Spirit, and that was the "becoming" (conceiving, gennao) that took place.
How did the Holy Spirit cause the conceiving? Through His divine power. Yet the child developed through the stages of pregnancy from implanted fetus through birth.