I agree. As has been much discussed in many contexts, recording time was stringently limited back then, but we can imagine that in performances, especially playing for dancing, jazz performers even of this early period could and did "stretch" out a song, especially if it was being well received, throwing in extra choruses and soloing around the front line. We can reasonably speculate that they used the same body language cues to signal players to solo and when to go into the last chorus that we see today (e.g., the two quick one-footed stomps which means "Let's all hit it for the rideout!"to make sure everyone "finished together" which everyone could feel even if they weren't watching the lead player).
We can't know for sure, but even in the ODJB's time bands in New Orleans had been playing for dancers and drinkers for decades and had to be able to stretch their repertoire to fit the circumstances. The players were improvising what they played in the ensemble sections (that's what makes it jazz), so soloing wouldn't be that different for them. After all, even classical music had a long tradition of soloing and featuring single section segment (horns, violins, woodwinds, etc.).