I can't help with why the 'shrooms are in a bowl, but there was Beangate on a local food group years ago that almost spilled into a sword-fight in real life over if baked beans should be allowed to touch anything else on the plate or if they must be in their own bowl. What's noted as being the best FEB in Pattaya (Smokin Joes) serves theirs in a little saucepan on the plate and that's the local standard these days.
Couldn't give a flying fuck personally, as long as they're on the plate somewhere!