Well... not all of the staff at DMV have the same level of knowing what they do. Like in CA DMV, even <Valid foreign passport stamped “Processed for I-551”> is listed on the proof of identity document on the website. When I applied for DL, the lady didn't say anything when she saw my visa and I551 stamp, and processed my application, however, when my wife went to get hers at the same DMV, the guy didn't know what I551 is, and even told us the visa was expired and couldn't do it, fortunately the lady sitting right next to him told him that because of the stamp, its valid proof for PRC for one year and the guy goes oh really? for sure? then again went back to ask for supervisor for double check...... speechless.