AS
Its not got to do with nationalities. Cockups occur in CAT as well as in Private as well as with ATC. As far as I have seen there is no safety benefits over FAA or EASA statistically only harmonisation between the two systems reduces the chance of mistakes
I fail to understand why ATC knowing something was wrong with the understanding of the clearance then recleared the aircraft to FL300 from FL200?
Surely they should have said " Climb immediately to 6000 feet (or whatever) on 1002 (or whatever) Read back
Their reaction was to reclear the aircraft from FL200 to FL300 which hardly indicates anything wrong or urgent
Pace