Just to clarify it wasn't a cruel 'tough love'. Lol, obviously no one wants for a child to pass out. Especially on a daycare providers watch. But I can't help but think if this child is so picky that they opt to not eat enough nutrition to make it through the day in an upright position then more attention needs to be drawn to the fact that something is off. I would wager that it is just that he hasn't been in the position long enough to NEED to eat foods he doesn't like...but perhaps there is a bigger issue that might not be identified if he is given just enough of what he wants to stay standing.
If it truly is a texture issue then there should be supports in place to help him over come that and to figure out what those issues are in place. The fact he seems so happy and healthy on all other fronts makes me think it is just a behavioral thing and not an autism spectrum or such as a root cause!
I wish you luck in making gains with him!! :-)