Has the definition of MLSS changed over the same period? 
I think though your second point is on the money though and is at the crux of the issue. We are trying to measure a physiological response with the human construct of minutes and seconds.
The same discussion can be had on the polarised training threads as well. Discussing whether the 8 minute (why not 7 mins 53 seconds?) intervals should be interspersed with 4 or 6 minutes of recovery is really a moot point. The intervals should be as long as you need to elicit the desired physiological effect and the recoveries long enough to recover and go again, which while similar for all, would all differ slightly between individuals.
I guess if we were able to measure these sensibly outside the lab this would be the advice we would all take to train optimally. I fully appreciate this applies to the FTP concept as well as you point out, but I’m not sure that nuanced view is well enough understood. It also isn’t helped by the desire of people to have an exact number to define themselves by based on a single data point.