No, those are not the capstone techs. I just checked my in-game tech tree and the capstone techs are things like Manufacturing Stimulus and Research Stimulus, which mention "Capstone" in their tooltips. Life Support Optimization is a tech that requires you to choose one of three techs, but you can only research one of the three. Xeno Biology is just a regular tech. Neither of those should be able to be researched more than once. If you have a saved game that can reproduce the problem I'd suggest you report it as a bug and supply the saved game through Dropbox or some other file sharing service.