A professional pilot is operating above through and below the level quoted and is in IMC throughout. That is why the topic was posted I believe and consequently it is also why that professional pilot could have pressed the PTT on hearing the clearance to transit at 2000ft VFR to pass that very useful piece of information that IMC conditions existed from 3000 or whatever down to 1200 or whatever.
And what exactly could ATC have done with such a piece of information?
Their remit extends to giving a VFR transit and asking the pilot to maintain VMC. Anything beyond that they can't do, and can't enforce.
Lots of pilots tell porkies about whether they are in VMC. It is routinely done by > 2000kg piston twin drivers to avoid Eurocontrol charges. In the UK, Class G, nobody really cares anyway and that is how the culture over here has developed. The other day I did a 150nm flight and changed VFR <-> IFR several times. I was under a radar service so I just told them, no big deal. But I don't think anybody actually cared.
What does your "professional pilot" label mean? Do you have to have a CPL, or an ATPL?