WTH does the Proximity integration create a proximity.* entity and not a sensor.* entity?

The proximity integration creates an entity of the “proximity” class. This means it cannot be used in blueprints and helpers which are expecting a sensor entity - e.g. A differentiate helper, which would calculate speed towards or away from a zone.

Why doesn’t the proximity integration just create a sensor entity? Isn’t it just a numerical sensor with some attributes?