My understand is, at the time of I-140 adjustment the posistion must exist. Once I-140 approved and I-485 pending over 180 days. There is nothing can hold you. AC21 is only useful if you get RFE on your I-485, right? As far as I see there is no requirement for the posistion existance or other requirement at the time of adjust I-485.
In extreme case
I-140 Approved
I-485 pending over 180 days, applicant was laid off on 181 day
EAD apporved
One can use EAD work for anybody (of course lawful) and including even stay home wait his/her I-485 approval. Your status is perfect legul. Only if RFE comes then one needs a sponsor to answer RFE, so called AC21. I would say once your I-140 done you are almost free. I-485 done, you are totally free.
In extreme case
I-140 Approved
I-485 pending over 180 days, applicant was laid off on 181 day
EAD apporved
One can use EAD work for anybody (of course lawful) and including even stay home wait his/her I-485 approval. Your status is perfect legul. Only if RFE comes then one needs a sponsor to answer RFE, so called AC21. I would say once your I-140 done you are almost free. I-485 done, you are totally free.