It's not unusual to have a boat registered in multiple states. Each state has requirements for how long a boat can reside in the state before it needs to be registered there. These requirements vary from state to state. If someone were snowbirding and taking the boat back and forth, this is commonly what would need to be done.
Boats under these conditions should get documented with the USCG so they don't need to run any bow numbers, then just post the registration stickers for each state. PO could have left the first states bow numbers and simply posted the reg sticker for the other states, though that is not how it is supposed to be done. The color for the state reg is usually different for documented vessels, but again this varies from state to state.