Probably right, and sorry for my contributions to these confusions... Keeping in mind I'm primarily a jazz outsider so my terminology is trying to describe bands I have been watching, and that terminology is pretty civilian.
For the first two bands I follow, the "era" I'm speaking of is pre-WW2, probably even pre-1935, and post WW1 -- Early jazz, old jazz, whatever...
With my (mis-) use of the term "small big band" ("S-B band" in some of my posts) I'm really trying to describe three 5 to 7 piece bands. These include trumpet, trombone, clarinet, tuba and drums for the earliest era "trad" band, and with trumpet, trombone, sax, clarinet, drums, guitar and DB for later era the "New Orleans" style band. The third band, probably post-ww2 era, has reso-guitar (amp'ed), vocals, trumpet, sax, drums and DB (amp'ed).
As mentioned these bands work 4 to 5 days a week at Disneyland and also take outside gigs. These are street bands and tend to do 15 to 30 minute sets 5 to 7 times a day. The "trad" band and the "New Orleans" style band do different songs all day long, while the post-ww2 band seems to repeat often during the day. I've never seen any of these bands with charts, and we've followed these bands for years, although judging by their expertise I'm sure they probably read fluently and could use them if they wanted to.
From all the responses I'm seeing it does seem that you have to be a jazz insider to really get the nuances of the types of jazz, including having an understanding the influences of various milestone artists to those types. At this point I'm not there; mostly I'm looking at jazz historically, roughly by date, as in an evolutionary process. Maybe that's not ever going to be very accurate, but it's where I am now.