A6 is pocket-sized only if your pockets agree

[paperhabit]

A6 gets called pocket-sized, but that depends on the pockets. It might fit while standing and still be awkward once you sit down. The size label doesn't tell you much about whether it'll be comfortable to carry all day.

[inkspilltea]

The cover can be the sneaky bit too: an A6 insert may fit, but a stiff cover or pen loop adds bulk. I judge it by whether I can get it back out easily, not just whether it goes in.