Quoting Yurka_Sanctuary, reply 3I believe it is working correctly. The selection circle is the space the Titan will occupy when it jumps. The entirety of the circle must stay within the limits for the Titan to successfully jump.
That is possible, but it makes the things unnecessary annoying. Sometimes you need to do the jump literally in exact second, cause its too late then (like when you are chasing fleeing enemy ships to eat them with your Maw), but you fail, as you slightly cross the purple circle.
Then don't fail. MWAAAAAHAHAHHAHAA.
Suggestion-wise, the purple circle should probably be retracted to the pinpoint limitation rather than expand for the full radial limitation. However, the occupation circle will still be necessary so you don't get the issue of existing in same space [aka trying to jump into another object]. This way, you would be able to do quick second jumps with easier limitation boundaries as most people are used to, while still knowing where your titan will be. It isn't a bug, but it should be changed.
As for Polistes, is it inside the purple circle, or 'just right at the edge' where the two circles would overlap? If they overlap even a bit, it could easily constitute 'outside of boundary'. But if anything, they need to change the radius of the purple circle and recode the selection system to only take the point as the limit rather than the full Titan.