Turns out that this program of having a number of Naval Reservists available for work in Naval shipyards has been around for some time and I should not have been surprised by anything more than the size of the recall. Here's a little background about the program and how it helps the Navy and the reservists in the SurgeMain:
You might note that in both those cases "60%" of the Selected Reserve billets for those rates were in the SurgeMain program as of 2009. Selected Reserve billets are the pay billets.
More information in this flier:
I am embarrassed by my previous lack of knowledge of this program - especially since it's been around for 14 or 15 years.