I am an existing Schwab account holder.
Earlier this year, I was given POA for someone else’s Schwab brokerage account. A month or two later, I checked and saw a hard pull from Schwab. I contacted Schwab and they said they hard pull was done because there was a Schwab checking account linked to the brokerage account.
So, be warned, even if it’s not your account and the account was already open, you are going to get a hard pull if you are added as POA on a Schwab account with a linked checking account.