Dozy;
Re no regs broken, well, if "the regs" are to be our only guide in terms of airmanship and good sense, one weeps.
The CEO's not endorsed, period; I find it tough to believe that there isn't some law against that.
FTR, I don't believe there is a high risk in this particular operation. Nor am I a regulatory guy, a frowning classroom monitor like the pompous eagle character on The Muppets. Nor am I even flying for a living now with all that goes with what is stuffed into pilots in the name of "procedures" these days and where common sense in flying an airplane has long since vacated the fix. All of what you point out was very likely in place and had anything gone wrong the guy in the right seat would have taken over while the seat exchange took place, etc.
Risky? You betcha, but a good outcome is very likely, (until/unless the inexperienced guy kicks/pushes/trips-falls-on something...)
That "nothing happened" is clearly not a supporting argument. Anyone unendorsed (and therefore untrained on type), or an unendorsed but current pilot who is in the front seat is a risk, period. Under the circumstances, I think it's just flying-club behaviour, and we're trying to grow away from that. What's it prove?
Ironically, it happens and will continue to happen because of best things about the pilot community - comradeship - we all want to share the genuine thrill and passion of what we love to do especially when it is a beautiful airplane, but for heaven's sake don't argue the case for doing so, because it can't be argued.
Re, "A CEO actually taking control of an aircraft? We don't even let our pilots do that." - EEngr
Now that is very funny.