Why do Jump and High Jump still have an movement lock?

[Andevom]

In 6.2, Jump and High Jump were altered so as to not physically move your character's location anymore.

That's not what the 6.2 update did. 6.2 made Mirage Dive a separate action rather than make it replace Jump/High Jump.

Both abilities still change your position, but it happens so fast now so you may not notice it. As per the tooltip:

Returns you to your original position after the attack is made.

That said, this particular feature often causes problems rather than providing any benefit. I think the only reason it's there is because Dragoons traditionally "return to where they jumped from" after landing their attack in other FF games.