It's not inexact when the data is at their fingertips. I saw Steve Kornacki repeatedly show screens with how the vote spreads were between Trump and Biden in '20 in the same areas where statewide races were being reported.
If the Dem was doing as well or better where Biden won, it was a reasonable supposition that it would continue going well for the Dem; ditto for the GOP candidate and Trump.
I admit it's a lot of data thrown up quickly and back and forth, but it's there.