Exactly, it's mainly the ion-cannon immunity that those are for. There is a way to do one form of quasi-deep knowledge raiding, though: basically go pick some weak AI planet that is adjacent to a bunch of other AI planets. Kill it, and build a command station there, giving yourself supply to that and all adjacent planets. Mine them all for knowledge while protecting your supply source on that planet, then abandon it when you are done.
I don't tend to do that, but if you're hurting for knowledge and have no other outlet, that's a way you can get a whole bunch in one go. It seems like there is always an easier way with a planet adjacent to mine, though. Building a bunch of science lab IIs and putting them into a transport, then sending the transport to the adjacent planet and way off into the ether, then releasing the science labs and keeping them heading into the ether... that tends to work without even taking out the ion cannons or snipers on the enemy planet. Bringing along a starship to run interference against any smaller ships that come after the labs can seal the deal, too.
