I'm sorry, but that's not true.
If the CM at the front desk sets things up properly, you 100% can have multiple cards. In fact, after a system upgrade about 5 years ago (presumably a precursor to the MDE/Magic Band implementation) it's even easier for the CM to set up multiple charge accounts. (Before, it was a very long and involved process that very few CM's knew how to do it)
We just did it this past November at both Riverside (three people, three different cards) and Saratoga Springs (four people, four different cards). The only "hiccup" was the day I stopped into the front desk to check on my own balance. At first the number she gave me was the combined total for everyone's accounts. After I picked my jaw up off the floor thinking I'd gone *way* over budget and how the heck was I going to pay all that, I found that it was combined. She then gave me just my own balance, as well as printed out the complete folios for all four individual accounts.
When checkout day came, I was emailed a copy of all four charge accounts, which were charged to the four individual credit cards just as they should have.
The problem isn't that it can't be done, it's having the CM set it up properly. Also, your best bet to minimize any possible issues is to *not* set up charging when you do online check-in and wait to do it all at the resort.
-Rob