My colleague recently bought a phone and also activated gift cards. There were about 10-12 of them (it was an iPhone 13 Pro) and there were no problems at all.
To be honest, that doesn't make you sound less likely to be a scammer.
But more to the point, it could easily be that it takes 15 or 20 cards within a short amount of time before the automated systems are triggered. Apple has a lot of data on how scammers operate, and has dealt with scammers many, many, many times, and probably continues to refine their checks periodically. Still assuming you are not a scammer, you are definitely unlucky.
