Nothing wrong with that. But… definitely not during a restore (and ideally not even during a OS update). USB devices can be everything. What they really are to the Mac depends on how they identify themselves. The Mac “learns” through drivers that are coming with a MacOS installation. As long as those are missing, the Mac has the problem not knowing what exactly is connected to the Mac. And this can lead to unexpected results. Even more so, if USB devices are connected through a hub, which makes stuff even more complicated.
I do not unplug every USB device during an update (who does…), but IF an error occurs, it is the first thing to be done before doing anything else.
EDIT: I have forgotten the most important thing: I am glad that everything is up and running again. 