Coggan has changed his tune over the years, which makes citing him problematic. It is so easy to get lost in academic debates on what is FTP and how to test it properly.
Moreover, this IMHO forgets the purpose of FTP in the context of structured training: it defines your power zones in structured training, and setting them correctly is particularly important for threshold workouts. Over/unders should really dip below and above your power at MLSS (see what I did there 
) to do what they are designed to do.
And no matter how you arrive at your FTP, you should validate it with (threshold) workouts (“Trust, but verify.”).
When you are fresh, then no. But there are situations where e. g. you are unable to complete workouts because of fatigue. That happens to me when I have had too much life stress and did three interval workouts per week. I’d often struggle with an otherwise doable interval workout. So context matters.
You, sir, are evil! 
