It shouldn't be to run away, as the interdiction mini game is there specifically to handle that.
I know players never want anything that is helping them win removed, but this is fundamentally broken. I know you just want to escape, but what is the point of interdiction if the absolutely best thing to do in every scenario is to not play it?
The interdiction mini game (when it works) works in favour of the more agile ship, which is going to be the pirate (unless it ignores a ships flight characteristics), so the 'escape' mechanism is stacked in favour of the pirate.
Im not saying the fsd cooldown should not perhaps be adjusted (though I think there are better ways to design this mechainc overall) but you're conclusion is, IMHO, incorrect. There is nothing fundamentally broken, unless you work from the priciple that the pirate should have a game mechanics advantage on top of the inherrent advantages they 'should' have by being a smart pirate.
If the pirate wins the interdiction they then have the confrontation stacked in their favour by all measures, they are in control, they are only attacking a target they have assessed and think they can beat, they have instigated the incident and have any advantage that confers. The trader is now spinning, has taken some damage, typically a cost already in excess of some pirates total rebuy and is now faced with a pirate who is either firing at them or demanding cargo.
I think short of a total redesign of the whole interdiction mechanic the thing should be left as it is or perhaps the cooldown of the FSD adjusted very slightly, though I have seen nothing to suggest this is the right solution at all especially as the interdictino mini game is already stacked in favour of the pirate. FD may say they did not anticipate the submit option being then used as a run away, but that DOES NOT MEAN they are going to change it to make it any more likely a pirate is going to have even more of an advantage