Paris is probably broadcasting on shortwave now that it's been rebuilt (Voice of Europe-style stuff), so the question is whether radio waves can enter the time bubble without being distorted to unintelligibility.

Also the problem of temporal paradox. If he's listening to a radio with Remilia and hears about the death of Perrine, for instance, that's going to be a massive problem when he rewinds. So it's best he doesn't know what's happening in the outside world.