Not only is it true that some folks can churn by getting instant approval and some folks can't, for some folks that works only sometimes and other times it doesn't.

I was able to churn for a while (got a second card while the first one was open). Tried that again 9 months later and was denied. Tried it again 6 months later, and was approved. Tried it again a year later, and was denied.

There is no clear pattern (at least none that I have been able to discern). The only pattern that seems well-established to be true is that instant approval=success, lack of instant approval=failure, but as pointed out upthread, it appears to be completely random whether one gets instant approval or not.

I, too, would jump at a business offer for more than the standard 25K signup. Of course, I have no idea if I would get instant approval.

Barclays is just unpredictable.