Slipstreaming SP1 into an SQL Server 2008 R2 Enterprise RTM.

When running the merge commands (to move SP1 files into the RTM equivalents) using robocopy [below] I'm seeing robocopy output that some files are "Older" whilst others are either "Newer" or "New File".

Should I be seeing any "Older" files though ?? How can I have an older file verson in SP1 vs. the RTM version? Is this RTM version not clean or something?? Anyone seen this before?

Thanks all...............