You offer a hilarious interpretation of BofA's business decision.

BofA found that buying AE miles didn't make economic sense, and is choosing to issue a different award currency. It's possible that an input to this decision is that consumers are beginning to find AE points less valuable, but maybe AE just raised the price.

Churning policies are unrelated to this (you can still churn cards in their new program). If BofA cared about churn, they'd address that separately.