I just did some testing with a former pro and he basically said the exact thing as this talk. I burn fat really well at low levels of exertion and then I switch to huge amounts of sugar as I move up in intensity. I have only trained at zone 4 or above for the past 3 years. He said that is a dead end road for racing. He advised zone 2 training, and stated that I will see physiological changes and become better/faster. He trains current pros and still races himself. In his mid 40's he is faster than when he was racing at the pro level. I have only given it a week so far, and mentally it is hard to go that slow. I rode at <130 HR for 2 hours yesterday, shifting down as soon as my HR started getting up. They only time I felt I could push a bit was going downhill. There is a group ride that I do that is super fast and super hard, I asked if that would be detrimental. Bottom line, I was told that I can train to train, or train to race. I am going with what he told me to do.

I questioned him about everything that I read is different than what he is telling me and that the video says to do. "lots of misinformation out there".

I had many follow-up questions after working with him, and this is the answer to one of them:
You mentioned your TT pace. Are you at zone 2 for a TT? In pro races when cruising along are those guys primarily in zone 2? and then kick it up when attacking, climbing, etc...?
Answer-
The normal tempo in Pro Tour is 5w/Kg. Yes, they are in Z2 here. The separation occurs at 5.5 paired down to 20 or so guys and then when you see the 2-3 guys off the front, that will be about 6.
In the domestic scene in States, the action here is at 4.5, so the levels are very different. TT’s are done in Z4. But my Z2 will be higher than most can sustain for 20min and I go all day long here as per definition.