Is it not possible that Coinbase just shut you down rather than bothering to get a bit more info? I really can't remember anyone noting demands for extra information like Bitstamp and others. You might trigger something and then it's goodnight no matter what.
yeah re suspicious activity that seems to be their MO. i appreciate their stance. if you trip up their risk analysis they have every right to stop doing business with you. that's a hell of a lot better than bitstamp's approach.
waking up one day to find your account closed definitely sucks though---especially because it can take weeks to get your money back. it's the same with banks though. they usually take a few weeks to send you a check when they close your account.
re going beyond the $10k daily withdrawal limit, i assume there are some additional KYC requirements. i'm just not sure what they are.
https://support.pro.coinbase.com/customer/en/portal/articles/2945311-limitsTo be considered for higher withdrawal limits, please go to your Limits page within Coinbase Pro and click Increase Limits.