Classic 41. Ask a simple question, get a straightforward answer, then argue when you don't like the answer. The data you have posted does not demonstrate what you think it does.

If you have not grossly overestimated your FTP, then you need to get to a medical doctor ASAP, because you have a serious medical problem. Or, you might have a lower level of aerobic fitness than you like to think you do. The second alternative involves swallowing some pride, but it fits the facts perfectly and much more elegantly than some mysterious undiagnosed cardiovascular problem.

There is no magic to riding at a moderate pace and talking. If you cannot talk, then it is not an moderate pace for you. Trying to redefine "moderate" because it feels good for your ego will not change how your body gets O2 to your muscles.