If it’s a scene by Trump&Vance to “justify” drying out of military support, then why would Zelensky participate in it.

Zelensky is interested in public support.

There doesn’t even have to be an agenda. It’s a press meeting as a conclusion to talks. As elected leaders and/or representatives it makes sense to participate.

If he wouldn’t have participated, how would that be better? They could still justify it - in even more of a vacuum to define their own views and spins. It would be worse.