A single bolt/screw can hold a lot of inline force. (and 'torquing' bolts creates a large inline tension in the bolt - many times more than what it holds in compression, which is why breaking them by over torquing is so easy - a thread is really a wedge and able to generate very high loads with small torques). Thread friction plays a role, and in some critical applications they measure overall bolt strain deformation and not torque. For thread shear, the bulk of the shear stresses are carried through a small number of threads.
Besides doing pressure vessel design for years, was sitting around drinking beer with some other engineers one day and wondering just how much a drywall screw could hold. So we drove a single drywall screw into the overhead rafters of my buddies shop and it lifted the entire rear end of his pickup.
Side forces, fatigue, and other factors are usually the cause of failures. In this example my fear would be me forgetting to take a bolt out (or something like that). So if Im lifting with a hydraulic lift I end up putting a lot more than the weight of the engine on it.
But really it comes down to other risk factors (in the ideal case it obviously works, but if something that you didnt think of happens to not be ideal then.... could be problems). If someone is willing to take the risk, this method obviously works. Others prefer a different method 'just in case' something goes wrong.
Thanks for posting. I will leave it to each individual to decide for themselves if they want to try it.
If anyone is interested here is a nice writeup on some basic principles:
https://www.fastenal.com/content/fed...t%20Design.pdf