I've catered, and worked high end banquet room, as well as on a corporate short order line.
It's expected in catering that food is prepared in bulk. Indeed, it would be highly impractical
to cook custom orders for a party of say, 150. That said, I never...ever precooked beef, be
it hamburgers, beef franks or steaks. Fresh gilled on site, even while the "first wave" were in line
getting served. Same applied to seafood and chicken breasts.
(and if there was no provision for cooking at the event site, I didn't provide steaks or chicken breasts
or burgers, they were compelled to order something else, like a beef dish in a sauce for instance, that
could be transported and held efficiently)
I did however, cook a grillful of burgers and hold them in chaffers in a light broth for 20 mins
or so. Acceptable....in that context. Thousands of burgers and I never got a single complaint.
Was this because its tastes "just as as good as fresh"? No. It's because it was expected.
It is not however, expected in a restaurant. If in doubt (and as suggested above) proceed how YOU
would want to be treated--would it bother you to find out your $10.99 burger plate had a pre-made patty,
for no other reason than the convenience of the kitchen staff?
If you're still unconvinced, cook a burger on your flattie, dunk it in your magic broth and hold for 20 mins,
all "nice and juicy". Then make a fresh patty med rare or med, and taste them both side by side,
just the meat, no bun etc. You'll see that despite being moist, the taste has changed.
If that still leaves you skeptical, serve it to someone else (fellow cook, your favorite server, etc)
in a "blind test" and see which one they'd rather fork up an Alexander for.
That said, even if there's not enough of a taste difference to make you a believer, there's an accepted
"code" of how things are done, in terms of what a paying customer expects. And people are accustomed
to feeling cheated and unhappy when shortcuts are taken with their order, even if it saves time and
keeps them from complaining about the time it DID take.
Makes it sound like they want their cake and eat it too huh?
Well they do--welcome to FSR's!
Bottom line, (again as said above) I would ask your Super,Chef, Km, or GM how they want it done.
And in a corporate chain, they have THEIR standards and you (and the store) are expected to stick to it.
Either way it's all on their shoulders... and you're just the cooker-upper.