I hadn’t thought of that. However the verb “receive” is in the aorist imperative active voice, which according to the Zodhiates means: “the aorist imperative denotes a command (yes), request (no), or entreaty(no). Unlike the present imperative it does not invoke a command ... for continuous or repetitive action. Instead it is often used for general exhortations and for things that must begin at that very moment.
Given the tense of the verb, and the context, I think it is quite clear they received the Holy Spirit as he spoke the words. Of course I’m no Greek expert.
I’m a long time Baptist, so in some ways your explanation might be convenient, but as yet I don’t think a careful study supports it.
**the aorist imperative denotes a command (yes),**
It was a command alright, but there was no indication that they received the Spirit at that moment. Nevertheless, they would definitely receive the gift of the Spirit in the near future, fulfilling the Lord’s command. And why would he command them to tarry in Jerusalem for the promised Spirit if they already had it?
Jesus Christ told Nicodemas that he needed to be born of water, and of the Spirit, explaining the “the wind bloweth where it listeth, and thou HEAREST the SOUND thereof, but CANST NOT tell whence it cometh, or whither it goeth: so is EVERY ONE that is born of the Spirit”. John 3:8
He also taught that “He that believeth on me, as the scripture hath said, out of his belly shall flow rivers of living water.” (But this spake he of the Spirit, which they that believe on him should receivce: for the Holy Ghost was not yet given; because that Jesus was not yet glorified) John 7:38,39
He told his disciples that “..if I go not away, the Comforter will not come unto you: but if I depart, I will SEND him unto you.” John 16:7
Well, he ascended up to heaven, and a few weeks later the Holy Ghost was indeed sent; and his church established.