The app isn't alerted. Rather apps can indicate they have sensitive information via FLAG_SECURE. This is useful in preventing things like your bank account info

The app isn't alerted. Rather apps can indicate they have sensitive information via FLAG_SECURE. This is useful in preventing things like your bank account information from persisting in the recents snapshots. Why this blocks manual screenshots with no override though is bonkers insane. But likely a case of an incomplete feature than malice as it's not unreasonable to assume both entry points for screenshots hit the same internal path.