I believe the whole idea behind the "I made this" achievements is that you do get to the required number crafting things one by one. If you were to multiply the yield of a craft by x amount, it would then also make sense to multiply the number of synths needed by the same amount in order to get the achievement, and we're right back to where we are now.
If the issue is time vs yield, I don't see how it will reduce it much if at all. You still have to the gather the same amount of base materials, and the amount of time it will take to increase progress and quality will be equal, if not greater than it would be to craft them one by one since were talking about an exponential amount of steps to complete the synthesis, each of which can come to a crossroads decision, adding time.
For intermediate mats like threads, cloths, nuggets, leathers, ingots etc. acquiring the base materials is where the ease comes in for you to make multiples, then it is all about getting the required craftsmanship and control to quick synth them. Removing the decision making process with quick synth will save you the most amount of time throughout your overall career as a crafter.
