No, it is not. My sister and I stayed in at BCV in December and they totally messed up the billing. I paid for my part of the dining plan with a gift card and she paid for her part with her credit card. I then set-up room charing with my credit card. I specifically asked them if her credit card was on file because I didn't want things charged to her credit card. They said no everything was alright. Well I don't know how they did it but everything somehow got charged back to her card. It was a major PITA to get it cleaned up.
With this experience plus other instances when I have tried to put cash down as a balance I have unfortuately come to the conclusion that most front desk CM's useless when it comes to these types of transactions. I feel bad for using that term but I know of no other. Part of me does not blame them. Most of the blame I feel lies with Disney for poor training. I have found it incredibly frustraighting. Going forward, I realize that I have to keep it simple for them. It is unfortunate that as a guest I am the one who has to adapt when there is really no reason. It is just not worth it to stand there, holding up the line, while it takes them forever to figure it out (and sometimes, in the end, it gets messed up anyway).