The duplicates in the 1000s are the new X1 range where they group channels by genre with locals in the 1000s, News in the 1100s, Diginets in the 1150s, sports in the 1200s, college sports in the 1300s, entertainment in the 1400s, Music in the 1600s, Kids in the 1700s, etc. Also anything that's exclusively in the 1000s is delivered over IP instead of QAM.
Even though most people have HD, until they upgrade ALL of their grandfathered customers still using SD settop boxes, contractually they have to carry SD duplicates, many channels also have terms that require them to be offered the same way their biggest competitor is offered (i.e. WBD/Turner will never let them drop the SD feeds of TNT and TBS as long as they still carry USA in SD). And instead of expanding the capacity on their systems to support more channels over QAM, most new channel additions over the past decade or so have been X1/IP only. Like in Philly, people with QAM/Cable Card tuners only get TV Land, Nick Jr, Nicktoons, MTV2, C-SPAN, BBC News, Sundance, FXX, AHC, Magnolia, Discovery Life, Discovery Family and a bunch of others in SD.
No network in the USA originates as 1080p, it's either 1080i, 720p or 480i. And Comcast is pretty much lying to their customers when they claim they can't do 1080i with H264 as that's how most C-Band feeds have originated for the past decade, and it's what DIRECTV, DISH and much of the rest of the world uses for HD.
Outside of NASA UHD, there are no 24/7 4K channels in the USA. ESPN/ABC, FOX Sports, NBC Sports, CBS Sports, NESN, Spectrum SportsNet and NBC Sports Chicago all use part time event only feeds, and premium channels like HBO and Showtime have no linear 4K feeds at all. Streaming providers like Fubo who give them dedicated slots just upconvert the HD feed the rest of the day.