I never saw, as a passenger, a catering crew in the cabin while I was boarding so no, boarding passengers is not done at the same time as catering.
However, baggage loading can be done together with catering (not on all airplanes, some have the cargo door too close to the service door, so the two vehicles won't fit together), to do this, we would have to split passengers and baggage into two separate services, which is a major change, and it will likely break existing 3rd party integrations, so it's not something that can be taken lightly.