Sol does have three habitable planets. Plus some moons, at a push.

Habitability isn't a Boolean. It's hugely dependent on history, context, and resources.

The more Boolean distinction doesn't have a name - but if it did, it would be something like Stable Evolutionary Potential.

Mars and Venus both fail on that. The moons fail on it now, but may pass when the Sun turns into a red giant.

The Earth has offered it for long time, with some uncertainty about the near future.

There's no reliable way to distinguish SEP at a distance. But noting that a star has planets in its habitable zone and making some estimate of how many planets in stable systems are likely to offer SEP is a decent start.