I don't use mechs but I would want the positive side of battery to the 510 pin cause my monkey brain can't handle the opposite for the same reason I can't eat a burger upside down or open chips bag upside down
So you don't use regulated single cell mods with positive down configuration or dual 18650 series mods, where the cells need to be inserted both positive up and down? Interesting.
A cell's wrap and top ring insulator always have to be in flawless condition no matter whether the mod is regulated or not, which negates the problem shown in the diagram above. That's why I double wrap all my cells, because shorts because of torn wraps can happen inside a regulated device as well, and no chip is able to prevent that.
But critical failures
inside a cell can always happen no matter the orientation of the cell. Even a slight shock from a mod or cell falling on the floor may cause a short inside the cell for example.
And the only way to minimize the risk of creating a bomb is for the cell to have a chance to vent properly.
Because of that, the statement "always positive up" is nonsense.
Btw, a cell venting its boiling and highly toxic internals straight into your face might not be very desireable as well.