Relying on only the parking brake like you describe is also dangerous. Put car in gear and/or use a wheel chock as well.

This was not on jacks, it's a small garage, but they raised the car on a proper lift

No amount of Reddit-ish always-isms and rules of thumb will make lifting and lowering objects this heavy not fraught with hand mangling peril if one is stupid or careless.

Chocks, deflating a tire or two, parking against a tree or another car with a working parking brake, ratchet strap through the wheel spokes to something solid, etc, etc, where there's a will there's a way.

given it was a mechanic garage they probably used a lift... or at least had some wheel chocks.

But yes, YT have plenty documentaries on that, together with "hydraulic jack is enough, I won't bother with jack stands"