I think you've mixed that one up, its usually something like "date the body, marry the glass", implying you'll buy and sell many camera bodies over time but keep good lenses. For non professional work you'd want to own both the body and lens, going to the rental shop every time you go on holiday or to a birthday party would be a pain.
For professional work you rent both the lens and the body so you can use the highest end gear specialized for the one particular job and aren't left hanging on to a $10k lens you use once a year.
> "date the body, marry the glass"
how is that different? They both mean that you won't be keeping the camera while holding onto the lenses. Also, at the time of the saying, it was for professional film shoots and not your take on vacay. Yes, it's an old saying, but rang true for a long time. Similar to Moore's law. Neither are as relevant while still being a bit truthy.
You don't rent the camera body any more than you rent the lens. If you are a hobbiest or doing a job that doesn't require a huge range of gear you should own both.
The saying is more that camera bodies get updated far more often than glass so you should care more about having great glass and swap out the camera bodies as needed. But owning lenses but no camera body would be absurd.
Again, isn't dating and renting equivalent?
Regardless, it is outdated when very few owned film cameras. If you had a chance to buy a set of Cooke lenses for a steal even though you didn't own a camera, you absolutely would if you were able. You could then rent a Red, Arri, or even film cameras as needed. You're forcing this into a modern digital only situation where camera bodies are dirt cheap maybe from being younger so that's your familiarity??