re: Rules question: Did Strall have to throw a pitch after the rain delay?

I don't think he would have to throw a pitch. But having been "announced" he was officially in the game. After that, whether he pitched or not, when removed he was no longer eligible.

The same thing with batters. Once announced, they don't have to officially bat. They can be replaced. But after being announced and then being replaced, they have entered and exited the game even if they never set foot in the batters box.