I guarantee you that there is not one person (possible exception of the AML officer) at Bitstamp who thinks that AML rules are good for business. They suck, but companies like Bitstamp straddle the fiat crypto divide and have to be seen to be absolutely on the ball with AML rules, for their own good.

It costs them money to verify your docs, risks upsetting customers and causes generally unpleasant feelings all round. It's just very unlikely that they aren't doing it for a good reason.

Perhaps someone tried to register with the same details. Would be worth asking them what triggered the check.