You're hitting two different kinds of fragmentation. One is physical file fragmentation (how many parts are scattered across the various physical disk strcutures), and the other is logical (within the disk segments you've been given, how organized/full are the data pages). These are largely independent of each other.

The SAN tends to somewhat muddy the discussion about the physical file fragmentation (with random access DB's, you might benefit from having your physical file stripes span a LOT of disk sets). The DMV is assessing the logcal fragmentation.