It is an actual charge that went through. I have encountered it with SPG as well. They told me that the FD goes through the accounts and charges any folio that has over 1k in charges because it is deemed a "high risk". Some hotels will not do it, but I have still experienced it many times. It makes for a really long folio when you do, as all the charges are shown as settled, reimbursed, and then settled again on a new account.