Actually, I don't consider it simply a matter of causing interest to be lost, but also a matter of delaying the start of open filking in what's usually the biggest room that any filkcon has available.

By the way, kudos to OVFF programming this year for concentrating the theme filks into a single room, making the rest of the space available for open filking. Theme filks can be fun, but too many of them scattered across the programming rooms can knock the energy out of the filking.