De-orbiting satellites I could see, but hijacking them seems more unlikely. Either they’re doing something physical to the satellite to hijack it (keep in mind every satellite is different, and this is an unmanned vehicle) or its over radio waves so why not do it from the ground?
Installing a modchip on a foreign satellite via robotic manipulation seems near impossible on the surface. Watching the Hubble service missions for example gives you an idea of just how much of a pain in the butt it is to service something in orbit, even when you have fully capable human beings doing the work. Building a robot to handle all of the unexpected hurdles of attempting such a task seems outside of our current capabilities. Even a waldo unit is a big ask.
Mostly because they aren't good enough yet. The manipulators struggle to balance small size, light weight, good grip, adequate cooling, and high strength. Getting the force feedback on the control solution correct is also difficult. And then you have to deal with communication delay as your bird is whipping around the world in LEO, constantly handing off between different ground stations, or worse, jumping through a sequence of Geo birds.
On the other hand, sometimes the government is willing to go to extreme lengths for intel purposes. The Glomar Explorer was outrageously ambitious, although ultimately only partially successful.
Even then you'd need intricate knowledge of the target satellite to hijack it - somehow opening and making electrical connections to a satellite you've never seen before seems rather infeasible - not even getting to the software side.
Nah I think it's far more likely it really was just a research vessel for more classified experiments they didn't want on the ISS.
