Here's how the devout group is
initially introduced. Prior to this verse they were not even mentioned, as I recall.
"Now there were staying in Jerusalem God-fearing Jews from every nation under heaven.
6When they heard this sound, a crowd came together in bewilderment,
because each one heard their own language being spoken."
That's a 1-stage event. They immediately understood what was being said because they immediately heard their own language. If this were the gift of 1Cor 14, the text would have gone something like this:
"The devout Jews heard words spoken in a language they did not recognize and could not understand. However, after that speech was finished, fortunately another speaker articulated an interpretation in their own language".
I don't know how to read it any other way. So you're right, it's not clear what I'm missing here.