As a PPL with several hundred hours (and no unapproved penetrations of controlled airspace) I would say that if this incident is true, then it is an unacceptable standard of airmanship.
Having flown in the US quite a bit, I am uncomfortable with medium/heavy and light traffic flying in close proximity and that is when it is under radar control: unapproved penetrations are simply not acceptable, although ATC seem to have been on the ball here and working to mitigate risk and the incident would appear to have been largely a non event in practical terms.
However, it does make one wonder about the logic behind the new NPPL which reduces the amount of training hours required to get a license.
Being an amateur pilot should include adopting a professional attitude and behaviours even if we pay for the privilege rather than get paid!