The issue is putting power back onto the grid. If power is out otherwise, the guys who come out to fix it want to assume there's no power on it. If someone's solar panels are still putting power into the local connection, it can be dangerous for those workers.

It is possible to have an automatic disconnection so that in a grid outage, your house will still be powered, but nothing is going out to the grid. They usually don't put those in unless you also have a battery backup. You may be able to ask your contractor to put one in, anyway.

This goes for generators, too. You're supposed to use a power transfer switch with those.