Bullshit. Striations are mostly genetic. Some BBers have striated glutes, others don't. Some guys have large spinal erectors but no deep striations, thats not a weak back. Of course you'll see some lower back detail on everyone when they are at extremely low BF but not everyone will have deep striations. You can see from that picture that Jay's lower back is dry as hell, same with Dexters...both are in excellent condition. It may be the pose & pic why you don't see a ton of development in either one in those shots.
You sir are right on the money ! striations are genetic as long as you do your part with conditioning . Whic is why some guys like Munzer have more in places that no one else has show and some guys don't despite being hard as nails & dry as hell