The vast majority of those bands and artists are not disco.
I don't know how you compiled that list, but there are a lot who don't belong there. Here is my breakdown:
ABBA - pop and pop rock, one or two songs mildly considered disco
Barry White - soul
Bay City Rollers- more or less teen pop, before disco craze
Bee Gees - didn't start out disco, but sure ended up that way. Then they sucked.
Blondie -more punk and new wave, a couple disco hits
Boney M - ??
Chic - pure disco, and like disco, they suck
David Bowie - glam rock
Donna Summer - disco queen, she didn't suck
Earth Wind & Fire -soul to rock, maybe a disco song or two
Garry Glitter - glam rock
Jackson 5 - soul and pop, ceased to exist in this form long before disco
John Paul Young- who??
Leif Garrett - no way. He was teen pop, like boy bands today.
Pointer Sisters- ehh, maybe maybe not
Rod Stewart -bluesy rock and pop artist with ONE hit considered disco
Roxy Music -art rock/glam rock
Sister Sledge- pure disco (and like disco they suck!)
Sly and the Family Stone- early 70's soul and r&b, broke up before disco
T Rex - glam rock!!
The Sweet - pop/rock, washed up before disco ever broke
The Village People- disco, and like disco, they suck
You forgot Gloria Gaynor. I could make you a list of pure disco 'artists' but I have to think awhile. Most of them have so faded that I can see their faces or hear their songs but their names escape me.
Disco, in its Studio 54, Saturday Night Fever stereotypical form only existed from 1975-80, with 78-79 being the biggest years. Several of the artists listed had their careers and burned out or faded away before those years, others were not disco or not purely disco. Some artists jumped on the bandwagon, even the Stones, but that doesn't make them 'disco' any more than it makes U2 disco for doing Discotheque.