Why is this not sorting?
Because you don't sort ballots. There is more to record on a ballot than just the presidential race, so simply putting two ballots in two bins would not be helpful.
Instead you tally ballots.
Sorting ballots also produces a pile that any corrupt worker would be able to identify as ballots that they want to get rid of, so sorting is considered bad election security.
Instead you should have a worker tally a stack of ballots. Then you give that stack to a separate worker, and they tally the ballots. If the tallies come out equal then you know that the tally was good and you add it to the master tally.
Election workers know that sorting is considered bad election security, so it doesn't happen unless something malicious is happening.