> 1. called is almost never used in practice (people just use .assert*)

Sorry but saying "almost never used" is not good enough. Not only because you hold incomplete data but because backwards compatibility is mainly binary: it breaks or it does not, and this breaks.

> 2. The is True / False is discouraged and is rarely used by itself, let alone in combination with .called

That is not true, is actually encouraged to check for singletons like True, False and None.