I am not sure where would it be appropriate to post it, so here it goes.
I have version 0.980E.
So the thing is, that luminosity of procedural supergiants does not correlate with this graph.
In other words, I think that luminosity/absolute magnitude of supergiants and hypergiants is too low in SE.
I've been searching for supergiant stars (luminosity class above Ib) in globular clusters, and found out, that absolute magnitude of Ib, Iab, Ia and 0 stars lingers around -3.7 and rarely gets above -4.
O and B main sequence stars however, follow the HR diagram well. So I wonder whether the super/hypergiant luminosity deficit is done on purpose or not.
Edit: Luminosity of supergiants outside of globular clusters seem fine.