Did it fit snugly?
So - you never got up there to clean it.
Is it the same electrician or not?
If it is, have it out with him.
I cannot comment on whether the circuit was satisfactory or not without knowing the details.
The new install looks fine.
In twenty years it might be filthy and falling to pieces.
Canopy hood inside a box - sealed on all sides. Why would I think to to clean inside it?
It's not the same electrician. The canopy hood installer was not the same trades person that build the kitchen extension or the conservatory. Two separate trades persons - two separate problems, if this third trades person is correct.