That is one of the things that makes SYSTM special - it’s there trademarked differentiator. They measure 4 power thresholds and indexes intervals individually to each. Where everyone else, I think, measures FTP and then estimates interval intensity levels from FTP.
If, by everyone else, you mean all the other online training platforms, then yes, most everyone else bases training intensity off FTP. Any coach worth his/her salt isn’t doing it that way, though.