Because it includes WATP doesn't mean it is based on WATP. The low impact aerobics option is an old one that was there before WATP was a thing. It is merely the best equivalent for that DVD as well. But aerobics, in general, is quite high intensity and I would estimate WATP to be on the lower side of equivalent to this.
Spark will include DVDs and fitness routines when someone else studies them and makes that data available. They don't have the resources to perform fitness studies themselves.
In the meantime, I would use "aerobics, low intensity" regardless of that it is also apparently similar to WATP.
Deb, in New Zealand