"Shouldn't Box 1 reflect a total of the two state wages ($15,250). Or, could there be a mistake."

Nope. That is fine. This is not a Split. It's informational reporting. As is being pointed out, each State has its rules, and especially with teleworking, you would see amounts that need to be reported by reason, such as Lives and Works In, vs Employed by, vs Temporary State of work locations (such as for utility workers or traveling nurses), etc. You could even see the full amount in every State listed. That isn't added together.