Yes it can but will take a little longer to heat up the room. If you hold a piece of copper pipe and pour boiling water over it the pipe will become hot and you will burn your hand a bit quicker than if you poured 80c onto a pipe and so on. I got A level physics many years ago in school lol. Its like putting the blower on in your car when the engine is not up to temperature, it will still heat the car at the temp set but take a little longer. Ultimately the aim is to be omfortable in your own home and if the flow temp needs upping there is no reason why you shouldn’t, but by doing so will decrease the efficiency of a A rated boiler to 75-80% which kind of defeats the object.
If you rads are balanced correctly there is no reason lowering the flow temp won’t heat your home. If they aren’t balanced correctly water will either gush through causing the rads to not heat up temp or cause some radiators to be cooler than others. The same applies to pump speed.