I think either you’ve got a calculation wrong somewhere or else you’re using a different definition of Zone 2 to what TR is using. E.g. Galena, a SS workout, has IF of 0.85 which is upper Tempo or Zone 3, not Zone 2.
So if you’re comparing SS intervals to steady state Tempo/Z3 rides, then I think SS gives a better benefit. Simply because you’re riding closer to your threshold and therefore triggering a greater training stimulus and adaptation.