I suspect the chef behind this plate presentation was either insane, or morally opposed to the consumption of veal:
I really dig a good vitello tonnato. It's admittedly not the prettiest dish, often winding up a little grey and flat. But in this case, since the champignons de Paris don't really add much to the flavor, I have to assume they were chosen for their visual effect, which, alongside the fleshy veal and the yellowish tonnato sauce, practically screams "severed ears." It's pretty lurid.
I won't mention the (otherwise great) restaurant it came from. And I can attest it tasted okay when you closed your eyes.