I really don't understand what all the negative hype is about over a FTRed SKS. If it's a shooter, so what if the numbers don't match.
The rifles were purposely designed, just like most milspec rifles, after the 1890s to have their parts be recycled into other firearms of the same type. Very expedient in the field, to strip reusable parts from a pooched, non repairable firearm and use them to put an otherwise serviceable rifle back into use.
I don't know of any nation in the world that did or does it differently.
Tolerances may not be perfect, but again, so what. They're just fine for the purpose they are intended for, which is to go bang, first time, every time, without fail, especially under stressful conditions.
I've seen and handled a lot of SKS rifles in my shooting life, well over fifty years. Some of them under stressful conditions. I've yet to see one fail to meet realistic expectations, UNLESS BUBBA GOT INTO THEM.
FTRs are part of a service rifles life and if it's done at a government approved facility, you are likely getting a rifle that's about as close to factory new as it can get.
I would be more concerned about a non FTRed, well used rifle, than a fresh FTR out of the crate, still in grease.
Some of the latest Chinese SKS rifles were well used and had never been through an FTR and it showed. I've even had a few brought in with parts broken and not the fault of the shooter. Part just badly worn or defective. One had a bunch of rust inside, all over the trigger/hammer group, which wasn't visible, until it came out of the stock.
Dealers aren't going to strip every rifle. That's why most of them provide a Caveat about these being military surplus and they aren't responsible for any issues they may have. Most will replace a defective rifle, repair it inhouse and put it back up for sale.
Thank goodness facilities like Lever Arms has or had a lot of spares.
If you're a collector, then purchase collector grade rifles. If you're a shooter, purchase the FTRs, there won't be any functional or realistic difference in performance.
If you're a shooter/collector, shooting your collectibles is contrary to what you're hoping to achieve and very quickly brings the premium price you paid, down to the level of the FTR and the only difference would be bragging rights.