"As used by Navy SEALs" means the manufacture gave some to a SEAL team once. It rarely means that the SEALs actually use them in operations.
I'd bet that 50% or more use the tough but cheap Ontario marine knife (basically a black KA-BAR), which they can get issued to them. Others will buy their own knives, or may be lucky enough to get the Navy to pay for one they want. These will be from a number of top *custom* knifemakers, not from any of the mass-production companies.
Don't get me wrong; for the things that most of us use a knife for, there's nothing wrong with production knives. But when you need a knife that has to take an incredible amount of ABUSE and survive (not necessarily unscathed), you need a tough, strong knife. And for the most part, that means a custom knife. Strider, TOPS, Mad Dog, and Randall are a few of the companies that make these knives.
-Troy