If I accept your opinion, I have the following question: a. You said: "the letter will show the conditions underlying I-140 petition STILL continues". As I said, I never submit any document related to my work; what is "STILL". Moreover, even unemployment person also can apply EB1A I-140. Logically when doing I-485, if he/she is STILL under employment, how can he/she submit employment letter?
b. What you said is the good explanation for employer-supported GC.
c. Do you have any web-site etc. for your saying? (I am looking for making sure)