This is incorrect. There is no hard limit, but having too many bands can cause issues.
Specialty bands are identical to the regular bands inside, but since they weren't setup with a hotel stay when they were first used, there can be issues because the hotel door locks are encoded onto the bands separately from the MDE account info. It only takes the front desk a moment to re-encode them, and it sometimes happens to bands that came with hotel stays as well. Encoding errors are probably the biggest issue with magic bands that the hotel front desks deal with.
Until mid-summer 2015 the reservation system would not consider guests to be "in-room" until the primary guest had tapped their band, or midnight. This was an issue, as for many families the kids always open the door the first few times. It wasn't a big deal, since it didn't affect anything important, but it screwed up the hotels remaining arrival counts for the day. This issue has been corrected and any guest entering the room changes the room status.
So here's the issue. The bands operate on two distinct systems. The first system is the custom-built MDE system. I haven't heard a limit to how many bands per person it can support, but it's practically unlimited. This means you can have 100 bands, choose one, go to the parks and expect it to work.
The other system is the hotel door locks. These are just standard Assa Abloy door locks, with a mickey head stuck on them. They are designed to be used in a standard hotel room, with a few guests in it. The issue arises when a family of DVC members shows up with 5 people and 22 bands each. The reservation system sends the list of authorized keys (bands and cards) to the door lock and sometimes they just freeze up or act completely unpredictably with that many authorized users. Deactivating the bands removes them from the list of keys and makes the door locks happy. The front desk staff I dealt with used a limit of 12 bands/cards, but there are a number of factors at play and this is just playing it safe. The KTTW cards did basically the same thing, but they weren't re-used so this was never a problem.