Absolutely correct you are.
I know of NO cartridges with a 1.4" case length that will perform as well as let alone out perform a 12ga 2.75" or 3" or 20 gauge 3" sabot shell fired out slug rifle with a fully rifled barrel.
In the right well practiced hands (like mine) under the correct conditions with the correct saboted slug ammo my Browning A-Bolt Slug hunter and my Marlin 512 Slugmaster are no BS honest 250 yard deer guns. Please do not ask me how much $$$ I spent finding the correct ammo to be competent out to 250 yards. Back when I did this sabot ammo was over $2 a round.
My longest ever kill with my A-Bolt was a LRF confirmed 245 yards, my 512 was 235 yards. Cant tell you accurately how many deer I killed between 150 and 220 yards with both guns but its double digits for both.
Heck my longest shot with my 12ga Wingmaster shooting 12ga 2.75" 1oz Active Foster slugs was 144 yards back in the early 90's.
I can honestly say the only man that I have ever met that shot more 12ga Foster and Sabot ammo than I was Mr. Doug Henderson. No one else I have ever met has shot even 1/10th as many 12 ga Foster and sabot shells as I have. At one time I had shot every Sabot shell sold by: Winchester, Remington, Federal, Lightfield, and Hornady. Won't allow myself to even consider adding up all the $$$ I sent down range in 12ga Sabot ammo.