You're saying that the ballots in the state are not sealed, they are reviewed first and then all are sealed as a certificate and sent to Congress. Individual elector ballots are not sealed, nor are they anonymous - everyone knows the vote of each elector.
-PJ
Yes, the Constitution requires the state include a list of what candidates received votes from the state. Which would preclude secret ballot.
But some states have secret ballot, which are then counted that same day by the state. So it wouldn’t be clear who the faithless Elector is.
Besides Washington state, there were 4 other faithless votes sent to Congress. Congress counted them.