first of all, the classifications are prob fine and likely not worth the energy to try and nitpick at fractions of a progression level
there’s probably more to determining progression levels than you think. I’d imagine it’s overall IF for workout, combined with length. Whorl may be 1:15, but 15mins are warm-up/cool down, while Pettit has 9mins warm-up/cool down and the progression level may focus more on the work periods. Of course Boarstone -2 is longer duration but less intensity.
Anyhow, this really isn’t worth sweating over at the end of the day and prob isn’t super productive to try and parse out the logic, it’s all kind of a wash.