The Phoenixpedia (sp?) entries for many (if not all - I forget, sorry!) researched items don’t display the text you saw upon completing the research. I think it would add flavour if it did (like in original X-Com), but this was actually an issue the other day: I was kitting out some stealth guys, and remembered (or thought I had read) that the Synedrion Pythagoras laser rifle was silent, although I couldn’t be sure if I had imagined this. I went to look it up, and of course - no deets.
this is a bug. The text is supposed to be there