PR.. I might be wrong but I think you are confusing the form number I-212 and INA section 212. Also, "voluntary departure" doesn't mean one left the country before removal proceeding began. "Voluntary departure" is one form of relief from deportation/removal. So, for example, if you were in removal proceedings, judge would give you the option of "voluntary departure", which means you would leave USA within a certain amount of time, and you will not be considered "deported" (although, the fact that you were in removal proceeding won't go away). This way, you won't face the consequences of being "removed/deported" (fox example, if you didn't take the option of "voluntary departure", and the judge found you removable) such as bans and what not. "Voluntary departure" is still a judge ordered option - it doesn't mean that someone just left the country.
So, if you want to re-enter USA after being in "removal proceedings", you file I-212, along with I-601.
On the other hand, one could be found inadmissible for many reasons listed in the INA section 212. For example, OPs wife could just leave USA before she is ever placed in "removal proceedings" - and before leaving if she accrued unlawful presence long enough to trigger a ban, she would be found inadmissible under section 212. Then she files I-601, which is an application for a waiver for grounds of inadmissibility under section 212 (and some other). This is completely different situation than the ones require filing I-212.
You are right, I just got a bit confused myself. I really meant the I-601 waiver and if necessary the I-212 if she ends up being removed/deported. Anyway OP needs to understand his wife does not qualify for adjustment of status with his present LPR status. Only persons under245(i) and immediate relatives of USC(spouse, parents, children < 21years), and persons who are in legal valid status can file the I-485.
She cannot remain here and get a GC while he is an LPR. He needs to ignore all forms and understand that she can only file the I-485 here if he becomes a USC. I-601 is difficult to get and is better he does not have to go that route.
I feel his pain but USCIS only understands extreme hardship.