As you can see there is a common size hole that will make a seal under moderate pressure but can't be trusted at 2000psi of an emergency braking situation.
I made this cross section of a test flare I made when dialing in my new tool to make perfect iso flares.
The red shows the internal pressure of the fluid the green shows the pressure from the "nut" fitting and the blue is the seat/sealing surface.
Notice that the red and blue push toward each other so the increase of pressure inside the pipe makes the seal tighter not looser.
Note how the example above is round no point. The tool used as directed did not make a proper flare I needed to start with the tubing not as far through the tool and ended up with a nearly perfect copy of the factory flare (right).
I'm hoping you had problems with the first tool because it was a single or double flare and somehow you got an iso inline tool to make a proper iso flare else you mated double to iso which is not a reliable connection for 2000psi.