Interesting research because it may confirm other information I have from the same era.
Not sure for how long semi-gloss was used, but keep in mind that prior to Duco paints in the late 20's, most enamels were not very glossy by our standards of today. However what was called Japan black and baked on was very glossy and my early'25 had lots of remnants of this on all black parts when I first restored it. And it proved remarkably resistant to paint strippers too.
The other information I have details factory changes for Willys Overland for the same years, and they introduced a matte finish during the model year, but it did not last long before switching back to higher gloss. A sales gimmick that did not take off? Maybe your reference might be highlighting that Chev also tried similar, but I would stick with gloss for your car. Lots of period photos show pretty good gloss levels on new cars from the cheapest to dearest.
