I have all type of 75mm Biotar and I had all kind of Helios 40 except latest newly made one.
Biotar 75mm is sharp wide open , can be awesome sharp depend from your focusing skill and luck , Helios 40 is not, sharpness is okay maximum , Biotar 75mm is perfect and safe to use at F2.0 Helios 40 at f2.8 very sharp too. Helios 40 I think more swirly than Biotar, I like Biotar swirly better. I still have earliest Helios 40 with serial 000233 , I sold all black Helios after try, Biotar 75mm slim is very small lens , Helios is a giant vs Biotar 75mm. I think they are different lenses not related to each other.