Counterpoint: I think this is a far better form of protest because it directly targets the party being protested against with a lesser impact on everyone else. It reminds me of a transport protest (I believe it was in Japan?) where the buses were working as normal but not collecting any fares from passengers.
When was the UK a part of the Schengen area?
I find it depends very much on where you live. Traveling within the Schengen generally involves less time due to no passport control and even less if your airport isn’t a busy one. I can usually get away with arriving 45 mins in advance (sometimes 30) and I’m out of the airport 20 minutes after touchdown.
Edit: I do agree with your thesis though.
If they’re not verifying the age, then surely a checkbox is enough?