What is the quality of Random class implementation in .NET?

I have two questions regarding implementation of Random class in .NET Framework 4.6 (code available here):

1. What is the rationale for setting Seed argument to 1 at the end of the constructor? It seems to be copy-pasted from Numerical Recipes in C (2nd Ed.) where it made some sense, but it doesn't have any in C#.

2. It is directly stated in the book (Numerical Recipes in C (2nd Ed.)) that inextp field is set to value 31 because: "The constant 31 is special; see Knuth". However, in the .NET implementation this field is set to value 21. Why? The rest of a code seems to closely follow the code from book except for this detail.