This is broken behavior, convention or no. The system is failing to flag/prevent behavior that works until the patch is reloaded. Just like it doesn’t allow you to connect invalid pin types, it should not allow you save a patch with an invalid name.
So it is bad because 1) it is silently accepting names that WILL cause a failure, breaking the user expectation of validity checking, and 2) breaking the user expectation that an OS valid file name would work, the case of every other application I know of!
vvvv is so good about this in other areas, this really is a glaring exception.