It's unusual yes, but it's not something that needs to seem concerning. Lots of things are unusual but not concerning, like taking up thimble collecting as a hobby, or having a child who grows up to be very tall. Relax, it'll be Ok, I'm sure she'll pick something.
And even if she doesn't, it just means a greater beaurocratic tangle to get him registered. It can be quite unpleasanat dealing with the fallout if you miss the 6 week deadline I hear, but that said she wouldn't be the first or the last to do it and it does all work out in the end.
I took the whole 6 to register my daughters and I am glad I did because I had time to privately make sure their names sat right with me. The result is I have no doubt in my choices at all, which is nice.
The little one's middle name was still a toss up between 3 options as I walked into the registra's office! Somehow or other though a name just came out when I was asked the question. It was the one her Dad had fallen in love with rather than the one I most wanted. But that was what I said and to my way of looking at it this means that was what was meant to be.
Don't worry, yes it's unusual, but it's also OK. It'll all come right in the end.