I think definitely not unique that I have to book through Citi again, that's been the case for me on Capital One as well, but is unique to Citi that

(a) they cannot confirm how much money I have on these credits, which I imagine could be annoying if you cancel more than one flight

(b) there's no self-service way to do it online and I instead have to call a call center to book. Capital One, and I think Chase, portals both have a section that reflects your credits and let you book online