I know you should never underestimate human stupidity but even taking that into account this still feels like security theatre on the part of PayPal.
If someone X is comfortable doing business with/as entity Y but a bank Z is not, it's totally sensible that X would say Y to the bank Z and bank Z would block them.
More importantly, "terrorists" is often used by some governments in reference to protesters or any group that they see as unfriendly to them.
Bottom line is: it happens, but I agree with you that people that know what they are doing are not putting "Pay for assasination by Osama Bin Laden on 03/28/23" in reference field.
Those of us “of a certain age,” will remember the old adage ”To err is human, but it takes a computer to really f*** things up.”