What is the Maximum Merge Articles in Merge Replication
The first link you provided is official documentation for SQL Server 2012.

http://msdn.microsoft.com/en-us/library/ms143432.aspx

The maximum number of articles supported in Merge Replication is 256.  This means that Microsoft will ensure up to 256 articles will work as expected.  I'm able to exceed 256 articles as well but I wouldn't do it in production.  You may want to consider splitting this up into multiple publications for production purposes.