Hi bMinor. While I realise you are looking at American comics, historically, there was a big variation in size and format in the comicbook output of other countries. If we take only English speaking countries, the UK, Australia and New Zealand produced all sorts of wrinkles, not simply the odd, occasional difference. Broadsheet, tabloid, pocket libraries, portrait, landscape, that strange Australian calendar shape they had for a short while, single tier strips, 68 pagers, 8 pagers. All sorts. The British WDL reprints of Dell titles are a bit smaller all round but feel thicker because of the thicker paper used - that includes the occasional thicker cover grade.
If we add historic European product to the mix, the mind boggles. Even pocket libraries differed in size, shape and page count. Finding sleeves for all these formats is sometimes impossible.
It's a great subject for research, and you get to read the books as well.
Hope I haven't bored you, but I am curious to see if other info is posted.