It does servers side checks, so if you need to craft a T4 and it does smart crafting starting with T1 materials, the T2s are crafted then form T3s and then finally your T4. But all those recursive crafts do server checks. I thought doing a bunch of T1s would cover my bases when I wanted to craft a bunch of T4s, which is true, except for the time factor. I should've figured this out after the first time in taking 16+ hours to craft a T4 Tachyon Deflector.
So I tried what I just proposed--give myself a bunch of T3s instead, so I can 1 click instant craft T4s. That worked better and I would mash the button 100+ times to craft 100x+ T4s. That starts really testing the RNGs to see if I can get legendaries. At the rate of taking hours to craft each T4, this wouldn't have been possible at all to keep re-rolling to try for Legendaries--unless you consider waiting hours each time scalable. So within the course of 2-3 hours I was able to craft legendaries.
I believe the delay is done due to server side checks to prevent people from "gifting" themselves legendaries/epics through exploits. By crafting T4s legitimately, I'm passing all server checks while getting my legendaries.