Just because it's the real world. :)

If things aren't segregated and the power goes off while I'm cooking, the aircon is running, the water heater is doing its thing, or whatever, then: I exceed 3kW.

3kW is the maximum that the device can supply. If load exceeds maximum, then something will (must) fail.

Hopefully it fails gracefully, but I mean: I've been married before and I understand how terrific and fantastic it can be when things go slightly wrong at home when I'm not around to address them. The less Rube Goldberg my creations are, the more peaceful my life is.

(None of this modern name-brand grid-tied stuff is any particular danger to linemen. It won't output anything on those terminals if it doesn't have an AC waveform to synchronize with.)