Well, if I order food from the Fat Duck[1], to name just one example, I expect the restaurant to prepare my food and not some "cook" in a container throwing together some stuff coming from trucks owned by a convenience food purveyor.

So yeah, I think it's shady and dishonest.

Sure, if a restaurant allows their brand to be used for such shenanigans they deserve all the bad press they may get.

Disclaimer: I use the Fat Duck as an example. I'm pretty sure they don't do home deliveries, let alone - Deliveroo.

[1] https://en.wikipedia.org/wiki/The_Fat_Duck