I believe I can explain why this happened - I think maybe it was inadvertent…
IIRC from a very long time ago, the letter shortcuts are generated automatically, they are not discreetly assigned. Starting from the left, it tries the first letter of each option name. If that letter is available - i.e. it hasn’t already been used by another option in the same line - it gets assigned. If the first letter has already been used by a previous option (further to the left), the second letter is tried, if it’s free, it’s assigned. If that one is also occupied, it tries the third, and so on.
Now, look at how the command line options have changed:
V5:
V6:
So, what happened?
In V5, the “P” was taken by “Previous”, and the “O” by “Object” - which, as numbers are not allowed as shortcuts, left “i” for 3Point…
In V6, CPlane Previous was renamed to “Undo” and that was moved to the end. That created a cascading effect as it left “P” as an available letter, which got picked up automatically by 3Point…