Here is a little more data supporting extended VO2max intervals at powers that are much, much less than what are traditionally considered to be VO2max power levels. In this case, as in the Bilat case, VO2max is maintained for minutes at a time at powers that are below, at, or just above ~FTP.
I’ve heard people say, ‘If you’re at or below FTP you can’t be at VO2max.’ While I understand how somebody might reasonably concoct such an unsupported hypothesis…there is a lot of accumulated data that prove that assertion wrong. If you do it correctly (hello all you hard start interval fans!) VO2max can certainly be maintained for a LONG TIME while work rate is held at or around FTP.
In the study I took these charts from they asked participants to do two ramp tests. The first was a traditional ramp test which they called ‘CIT’. The second used VO2max data from the CIT & manual adjustment of work rate to hold participants at VO2max after VO2max was achieved. The kind of thing that’s so tortuous it makes you wonder how the study made it past ethics review. 
Also worth noting…most subjects in this study achieved a VO2 plateau during the traditional ramp test. Somebody once told me that if your VO2 plateau’s prior to failure on a ramp test…then something is wrong with your heart. Well, for some participants in this study VO2 reached a plateau prior to ramp test failure…for some it did not. So I can see how you might come to that misinformed opinion if you aren’t used to looking at a lot of data…maybe if all you’ve ever seen are your own tests or something. Definitely, though, subjects can reach a plateau in oxygen consumption, continue to pedal at that plateau for some time, then be unable to continue the ramp test.
Just some interesting stuff that made me think of this thread.