I don't know if they changed crafting in a recent patch I did not see, but my understanding was that +1/+2/+3 simply improved the chances of HQ outputs (number or quality depending on method used) as a HQ ingredient.
Again, if they since changed that please disregard.
^This.
Regardless of the quality it can still be used in the same recipe. All it does is provide a higher base quality/durability to a synth for a higher chance to HQ.