Even if we were to accept that as more than a marketing tool, (Oh, lookee, this car has McPherson strut suspension, it must be good):
1) 600 is a lot less than 1000 or 1500, denier numbers commonly found on luggage
2) '600' tells us nothing about the weave or the number of layers.
3) '600' tells us nothing about zipper quality, stitching quality or anything much else really
so I see no reason to be able to say that an advertised number of '600' tells us the bag should be fine.
AFAICT that bag is no better than the several torn-through ones I've thrown away.