That is definitely strange it would not let you change the name and default to the first name on the deed.
I registered last week since I have a DLH reservation. I have 2 memberships (one a mix of resale/direct points and one resale only). When I tried my blue card ID, it would not work, but did with my white card (someone else had the same thing happen in this thread). So, I called MS yesterday and they did some checking and confirmed I am for sure on the list for that night and as long as I can produce a digital card in the wallet for Direct, I will have no problems getting in. Tried to get in the queue today to book with my other ID and I kept getting that early registration was over and it would not work. No big deal since we are good for that night now.