Okay, so you think that when people say "sex is a spectrum" they literally mean "sex has more than two categories which can be plotted in any order" rather than "sex takes on values in between male and female." I don't think that is what they are claiming, but okay. If that really is what they are saying, your pie chart appears to bear them out. Since any pie chart can be converted into a bar chart, you must admit that reproductive classes are indeed a spectrum.
Haven't got the foggiest idea what "people" (which people?) mean when they say "sex is a spectrum" - most of them, like Novella and Shermer, just throw a a bunch of "stuff" at the wall and say, "behold, a spectrum!"
For example see the former's kick at that kitty which uses this graphic to start the ball rolling:
https://sciencebasedmedicine.org/the-science-of-biological-sex/
I'm surprised that "science-based medicine" doesn't stick in his throat, but it should. In any case, he at least is using "male" and "female" as intermediate points on his "sex spectrum" with the end points drifting off into never-never-land. Idiots - being charitable.
Though I haven't the foggiest idea what're getting when you insist that I "must admit that reproductive classes are indeed a spectrum". Some reason to think you're not paying attention ...

since I've clearly said that the spectrum of three
reproductive classes consists of 3 and only 3 members: male, female, and sexless:
Of course I admit that "reproduction classes" is a spectrum, but I am most certainly not saying that each sex is a spectrum.
After all this going around about which definition to assign to "spectrum," we're left with the following:
1) Attempting to classify people using Steerman's interpretation of sex yields three categories, which could be plotted as a bar chart with categories in any order and is thus a "spectrum," for some values of the term.
2) Attempting to classify people using Hilton's interpretation of sex yields three categories, which could be plotted as a bar chart with categories in any order and is thus a "spectrum," for some values of the term.
3) One of these approaches is clearly better, because reasons having to do with spectra.
This is not a syllogism, I just like groups of three. Behold, another spectrum!
Again, it looks like you're not paying attention or you're intentionally trying to muddy the waters. Reproductive classes constitutes a spectrum of three - male, female, and sexless. But that is not saying that each sex is a spectrum; that is Hilton's argument, not mine.
It's not a case of either 1 or 2, but of 1 and not 2. That is, it's perfectly reasonable and justifiable to say that reproductive classes is a spectrum, but it is not justifiable to say that each sex is a spectrum.
Do pay attention there Double-Oh Seven ...