You're not being charitable enough to the comment... you two are in completely agreement with one another if you only changed the meaning of the word "main". It's clear the grandparent meant "the thread that's doing the work."
It's really difficult to get to that meaning, because "main thread" is what you call the thread where main() is invoked and which is where all the GUI calls must happen. You can't use a common term in context to mean something different from its common meaning and expect people to follow.
And yet it was perfectly obvious what was meant. If you just assume the person who made the comment is not stupid/rambling (difficult concept, I know...) it is not difficult to get the meaning at all.
You say it was perfectly obvious, I say it's almost impossible for someone steeped in iOS development to understand any way other than the way I said. Even given a huge amount of charity to the poster, the best I can do is "I have no idea what they mean by this."
How come we have to give this person the benefit of the doubt to the point of understanding a term to mean its exact opposite, but you don't have to give us any of that?
I think it's just a "my environment" bias thing going. I don't work on iOS and I immediately understood what was meant by the comment. Of course, the "my environment" bias may also include a degree of the "other" is not as bright as me.
Changing a fundamentally well-defined term (main thread, i.e. the one on which main() is called which is running the core event loop for the application process) to be an incorrect opposite is rather fundamental when one is explaining an iOS best practice.
