Titebond 3 front label says it is stronger but the back label in the instructions caution about using the glue where there will be any stress. So, they get their advertising in to get you to buy it and also caution you against using it anywhere it might matter.
None of the Titebonds (1, 2, or 3) are totally water proof. Do a test and put some dried glue in some water and see what happens. It swells the glue and makes a gummy gooey mess.
You are correct......none of them are totally waterproof. Then again, neither is hide glue. Regardless, I don't take my instruments out in a downpour, let them swim around in the sink, or float around in the bottom of a wet boat. So, my favorites still are Titebond original, Elmers Carpenters glue, or hide glue. YYMV, Dave Fox