It is a good exercise, but in practice, what's the big deal?
Even if the app is bulletproof, age verification will get bypassed. Account sharing, file sharing, darknets, etc... It mostly prevents kids from stumbling upon content that isn't meant for them, but it won't resist deliberate attacks for long, especially if the parents are complacent. And for that, the EU Age Verification app looks fine, especially now what the easy bugs are fixed.
How Paul Moore broke the EU age verification app in 2 minutes, the 8 confirmed vulnerabilities and the emergency patch 24 hours later. Full analysis.
For the same reason, I don't use sudo. Despite being patched, the presence of prior vulnerabilities [1] and hacks makes it fundamentally not trustworthy.
1. https://app.opencve.io/cve/?vendor=sudo_project