A “regular bed” has always been an 8ft bed for the last 60-odd years. Look at any full-sized Ford, GMC, AMC, or Chevrolet pickup from the 70s, 80s, or 90s – it’s nearly impossible to find one with anything but an 8ft bed. If you wanted anything shorter you went with a “toy truck” like the Mazda B2000 to B2600i, or a Toyota Tacoma.
It’s just the utter lack of 8ft beds in full-sized modern (last 10-15 years) trucks that has had the industry reclassifying uselessly lobotomized truck beds as “regular” and normal-length beds as “extended”
It’s the 9ft bed you could get as an option on full-sized trucks above the base model. So for Ford, the F-150 was stuck with either the regular 8ft bed - which was the default - or could go down to a 6.5ft short bed, but for the F-250, F-350 and higher, you could go for a 9ft long bed.
In some model years, the F-250 & 350 even had its rear axle shifted further towards the rear by a few inches when choosing the long bed in order to get better balance for loads.
This 9ft long bed was even marketed as a “large camper bed” for those oversized slide-in campers that were too long to allow a standard 8ft bed to raise its tailgate. This was a problem with 8ft beds, because a permanently-lowered tailgate could obstruct the license plate, necessitating its removal so the plate was more visible. The long bed didn’t have this problem, and the tailgate could stay on.