I said what I said.

An in-home fitness service using Gymkit to provide deep integration with streamed workouts.

Their non-equipment workouts work with Healthkit, but to have parity you need Gymkit too since Apple Fitness is not just about equipment-less workouts:

https://www.apple.com/apple-fitness-plus/equipment/

To that end it's more deeply integrated than Apple Fitness since Apple Fitness streaming content needs to target any Gymkit enabled (or really any hardware period) hardware of a given type with all the variation that entails.

This company is customizing the stream for a handful of Gymkit enabled devices which gives them more control over the workout experience