Well the new movies are with the EU in mind so I’m pretty sure it was never intended to be an actual sub-plot.
(For all we know the story group may have added it all once it was decided to give Dr. Evazan a cameo.)
There was a bounty hunter (triangle face) tracking Dr.Evanzan and Walrus what ever his name is. So I think although it feels like Fan service without any real reason it’s likely that Jyn bumps in to him just as triangle face is going to shoot them then the tank battle happens so they get away. as Triangle face is behind the tank as it rolls past and cut off from pursuing.
So it’s cut down quite a bit, and does not really flesh out Triangle Face tracking the 2 criminals which would come prior to Jyn bumping into him.
It’s a guess but it’s very likely more to that sequence.