Just to give a few more details about this from a Steelers follower - and yeah, I like Pickett more than most, but this is mainly coming from someone very frustrated with how the Steelers do business -
It wasn't going to be a competition. The last time the Steelers ran a competition, in 2022, the Steelers said it was a competition then didn't allow Rudolph or Pickett to compete with Trubisky all summer. He started with the 1sts and nobody else got a chance with them.
So when this happened...
He thought "I've seen this movie before". Also believed to be part of why Rudolph allegedly wanted nothing to do with coming back to the Steelers after playing his way into having options.
Also, and this is coming from a Pittsburgh sports site of so-so veracity (but then there's no reliable insiders on Pittsburgh sports including the people who originally reported this) in
DKPittsburghSports, but allegedly the real story on this
Apparently the real story is that Pickett believed he would either start or not dress that week. Since Rudolph had been named as starter for the Seattle game, and Pickett had neither been medically cleared to start or been going through the regimen he'd have needed in order to play that week.
So when Pickett arrived in Seattle to find his stall had been set up, he and all the other QBs were very confused. Pickett asks Tomlin for a meeting to clear this up. Tomlin immediately declares that Trubisky is number two and Pickett isn't dressing, and Pickett isn't named as emergency QB because either Tomlin didn't think about it/Pickett would have had to take painkilling injections before hand (the sources didn't know that bit for sure).
Caveat emptor.
In any case, there's ample reason for Pickett to be very frustrated with the Steelers (not even going into the miserable two years history here) and he's gone from back-up in an org that's crap with QBs and offence to one that's pretty good with those things.
I don't know whether he'll be any good for them, but assuming the talent around him can lift him, he'll at least be better than he was in the Steelers.