Ah - the old 'safety pilot' argument!
Here's what the ANO says:
From the ANO, 'simulated instrument flight conditions' means
a flight during which mechanical or optical devices are used in order to reduce the field of vision or the range of visibility from the cockpit of the aircraft.
Those bits of tin so beloved of the CAA or foggles, for example.
If you can find a legal definition of 'practice instrument approach', do tell us - there's nothing in the ANO as far as I'm aware.
The problem with flying IFR approaches in VMC
outside CAS is that, if you're on your own head-down on the dials, no-one is looking out to spot other aircraft and take the relevant 'see and avoid' action in accordance with Rules of the Air. Although if you're using a decent autopilot, it'd be a different matter, of course. But in reality, the rule regarding 'practice instrument approaches' would be impossible to enforce.