Quick sanity check: are these items being disassembled on a world where you possess research labs? I seem to remember some issues with disassembling captured technology and bringing the research points back to the home world...
Or I could simply be losing what's left of my mind.
Yeah, of course I am that sane.
My problem was the following: Normally, when you dissemble a component with unknown (but accessible) technology you get i) notified in the event log that you gain some research points, and ii) in the research overview tab it gets displayed as something like 28500/30000, indicating that 28500 research points must be spent on this project, out of the original 30000 (i.e. you gained 1500 points in this example). Exactly as happens when you savage a wreck, or chancel a research project.
Now with compressed fuel tanks the event log still recognizes that you gain research points on dissembling them. However, afterwards the research tab does not show that you have already gained some research points on the project. That is not quite surprising, as compressed fuel tanks are not an “available” project to begin with. You can only see the research project at all by clicking on the “all” checkbox, where you see that the project costs a total of 1000 research points – but not how many rp you have gained already from dissembling.