Best buy requiring passcode to "verify" if a screen replacement works?

I recently had my screen replaced at Best Buy, Apple's authorized repair center and the rep there asked me to write down my passcode so he could "run diagnostics". As of IOS 10.3 or so, any authorized center can run diagnostics without it being unlocked.

I wrote it down to get going because they insisted they needed it to verify the repair, the rep took the post-it back and after about 5 minutes came out with my unlocked on the home screen.

Is this normal practice? Apple is big on security but I find it hard to believe that this is normal practice.