Yep, the screw-ins are pretty strong, but aren't really intended massive loads.
Having said that I've been able to lift the entire kayak (Revo) using two of the shock-cord ends and 8mm bungee - more of a test than anything else.
However, I usually go with stainless screws/nuts and nylon cutting-board for backing, which makes everything very secure.
For my Mirage drive leash, I use a shortish (about 1.8m) heavy-duty coiled paddle-leash attached to the hull via a screw-in pad-eye on the front left hand hatch bungee:
I found this a better solution than the Hobie offering - it's much shorter and doesn't get in the way, but it still allows full access to the drive (for any potential on-water maintenance) while seated.