Looking to migration a 5.1 server to a 6.5.5 server.

The 6.5.5 server was built to be the destination server - bare bones - no
additional products and installed in it's own tree.

When looking at the instructions for Migration Wizard, it mentions that the
destination should be build with the Pre-migration server pattern. This was
not the case for the server that was it built, it was built custom.

The destination is all done, is it necessary to rebuild it with the
pre-migration pattern? What does it accomplish ?