Have you done it with a dynamic statement before?

MSDN mentioned the following:
When using FillSchema, the .NET Framework Data Provider for SQL Server appends a FOR BROWSE clause to the statement being executed. The user should be aware of potential side effects, such as interference with the use of SET FMTONLY ON statements. See SQL Server Books Online for more information.
Not sure if that would impact what you are doing though. It does hit it has to put it in there somewhere an it seems you are excuting a sp to just execute a "dynamic" sp.