Again with the complaining for an Empire that is evil? Really?
They blow up a planet to prove a point killing billions, then there is this. I don't see how it being somehow coincidental is a mark against the episode. Kallus is an ISB agent, and likely given command over certain Imperial Navy operations, especially if they involve Imperial security matters, like oh... I don't know, a potentially rebellious or dangerous planet? And it is a known fact that the empire does not look kindly on aliens.
If this raised your eyebrow a bit, that's fine. But I have to wonder if stuff in the original trilogy did as well. Like say... Vader being the iconic villain who chokes people with magic, fights with a red laser sword. Then, at the climax when their battle station is under attack, he hops in a Tie Fighter to try and stop them himself, because
of course he's a pilot, too! And an exceptional one to boot. This kind of stuff isn't new to Star Wars.
I understand that it's nice to look at the Empire and want to have a few people there that satisfy your cravings for that moral grey area. It would be nice, but only if it's done well, and the character is not tampered with like a certain one in The Clone Wars that they tried something similar with.
The Empire are space Nazis, and their propaganda permeates everything in their training programs. Tie Pilots, AT AT drivers, Stormtroopers, etc.
What you want is this.
But that might not be what they're going for with this show, and that's okay. And if contrivances or coincidences are a concern to you, how contrived would it be that the crew of the Ghost just happened to run into that guy?