Are you sure your passport wasn’t checked?
What you’re describing sounds like it was the customs check. Pre-brexit, if you were arriving from the EU, then there was no customs check since we were all part of the same customs union.
The usual flow is
immigration check -> baggage collection -> customs check
Even if they did check his passport, he didn't have an EU passport so probably shouldn't have been allowed to skip customs.
Yeah wasn’t checked. I’m pretty sure it was a smaller airport than Heathrow. I definitely went through the wrong path out