I had the case of so called "future employment"(gc is meant for future employment but what i could infer is i didn't work for the petitioner during filing of my labor and I-140) but was approved by service center directly although with 2 RFEs.I can site many examples where ppl got 485 approved directly from service centers in future employment cases.
Now-a-days, USCIS to reduce backlog will randomly transfer cases to local office.
In my case i joined the GC sponsorer right after 140 approval and 2 mos. ago USCIS asked EVL from my employer.
In their 485 approval guidelines , six flags are mentioned for cases which requires further scrutiny or interview, thats not the case now-a-days.
But for some issues like arrest,class a/b medical conditions,apparent fraud,out of status etc, the chances are almost 99.99% that the cases will find refuge in local office.
Search in the forum for similar topics and you will find handful of those.