The first 13 minutes or so a standard ramp test are so easy that I can’t imagine its really doing anything but thoroughly warming your legs up. I understand there’s a need to drain your anaerobic capacity, but I wonder if simply starting the ramp after a few minutes at FTP (after a few minutes at Z2 to warm the legs up) wouldn’t take care of that.
You could probably afford to knock the first three or so minutes off, though. I wonder if there’s a specific reason for starting at that particular % of FTP.
I don’t think you’ll find any science behind it. The start was arbitrary and the ladder is a certain % of ftp per minute. Once the test was setup, they studied the riders to extrapolate the ftp formula.
I have little doubt you could design the first ten minutes any number of ways, you would just have to do the same extended testing period to figure out the formula from there. But what would be the point? The test takes less than half an hour as it is.