I try not to get too hung up on definitions about that sort of thing since it tends to lead to a lot of silly arguments and gatekeeping(see UL type forums) the carryon only thing is mostly the draw for me anyway. I typically take two bags, a Porter 46 and a small backpack that typically is a personal item/daypack/hiking bag. Usually the small backpack would fit inside the porter, but not always depending on what all is going.
I try not to get too hung up on definitions about that sort of thing since it tends to lead to a lot of silly arguments and gatekeeping(see UL type forums) the carryon only thing is mostly the draw for me anyway. I typically take two bags, a Porter 46 and a small backpack that typically is a personal item/daypack/hiking bag. Usually the small backpack would fit inside the porter, but not always depending on what all is going.