Can one of the phases be supplied from the generator?

Sergey asks:

Good afternoon. There is an input of 3 phases into the house. All wiring in the house is distributed over 3 phases. We introduce a backup source into the house - an 8 kW generator. The house has equipment that uses several phases:
1. The boiler (uses 3 phases, according to the instructions it can be connected to 220 by connecting the inputs with a jumper. There are 3 heating elements, each one eats from its own phase. zero is present).
2. Hob (uses 2 phases, you can also short-circuit with a jumper and use 1, according to the instructions)

The question is (I understand the logical answer to it, but nevertheless, "ochuchuyu") - you can, after all, using changeover switch, when switching to the generator, feed it into the home network in 3 phases - one s generator? those. simply by connecting a jumper in a three-phase switch-disconnector the inputs from the generators. and so on. one phase will go into these 3 wires. This will not affect the operation of the equipment, will it? in fact, that I will jump in the phase device itself, that this will be done in the dashboard - the result will not change, right?