As Mel mentioned in that article, the misnomer calyx started with that same book and that Robert apologized years later for introducing that incorrect usage. So that books is in this context the worst reference - despite its name it's not an authoritative source on the structure of cannabis flowers.
Pic shows the stigmas. From a distance it looks like a style with stigmas but as you can see if you look closely the stigmas together form the hair most call pistil. Leaving out the ovary is imo not just a slight difference, especially combined with the misused term 'calyx'.
Cannabis growers have their own terminology yes but the terms pistil, stigma, and style, and calyx and bracts etc refer to the basic flower structure model used to identify all flowers on the planet and in that regards Cannabis Sativa L. does not have a special meaning (there's no misconception amongst botanist and growers concerned with hemp or researchers concerned with the drug variety). What it does have is a huge misinformed following and because of prohibition a lack of professional botanists, authors and educators publishing accurate information.
The misuse of calyx and pistil are good examples of parroting. For those a little more interested than that it's essential to know the correct terminology. Basics like like stigmas receive pollen, seeds grow in a pistil, bracts enclose the pistil and are covered with trichs, male flowers have a calyx. Etc. etc.
I don't expect or suggest cannabis growers suddenly start using the correct terminology, I just think it's good to be aware of the fact they are misnomers. Although, if you ditch calyx, it needs its own name back...
https://www.rollitup.org/t/my-1st-hermie-am-i-right.837031/
Reading my reply there just makes me laugh... pistils coming out of calyxes... lol
That thread contains good pictures of "pistils". Pistils without a bract (hence no trichs). Nr. 6 in the drawing I posted earlier above.
Here's another one:
The hemp flower is pistil with bract, next to it is the pistil. Two hairs straight out of a seed... not really, but that's what it looks like, especially if you stick with invalid terminology.