R&D tech pool does increase the effective design year of the parts.
The quality slider does that too, but also adds flat bonuses to certain stats.
That is why the quality slider is more powerful than tech pool by itself, but also that means the two effects can’t be rolled into one single number - and yes, I agree that the way it is displayed in the UI makes it seem as if they are the same thing to some degree. Something for me to consider for 4.2!
Cheers