I recall using 1" squares to represent 5 foot of dungeon floor going at least as far back as '86 or '87, when I ran Keep on the Borderlands for what had to be the third or so time. Dave ran a barbarian named Bubba, using a local version of the barbarian class built using Paul Crabaugh's golden "Customized Classes" article from Dragon #109 and Eric played an elf that was always blasting stuff with attack spells. I don't recall the rest of the party. Anyway, we drew out the floor plan of the Caves of Chaos on a battlemat. I've ran way more games without maps and minis than with, but whenever I've done D&D with figures I've always used this scale.
"Figure bases are necessarily broad in order to assure will stand in their proper position and not constantly be falling over. Because of this, it is usually necessary to use a ground scale twice that of the actual scale for HO, and squares of about 1 actual inch per side are suggested. Each ground scale inch can then be used to equal 3½ linear feet, so a 10' wide scale corridor is 3 actual inches in width and shown as 3 separate squares. This allows depiction of the typical array of three figures abreast..."
(page 10, emphasis mine)
Before I started taking the battlegrid super seriously in 3e, my dungeon maps had a fair number of crappy little 10' by 10' rooms. But a four by four square is no place to have a battle. 3 x 3 is slightly better in this regards. Also, a smaller scale means that doors that are one square wide aren't so dang massive. And the prospect of a three abreast down 10' corridors changes the dynamic of dungeon crawling. You could put a henchloser with a ten foot pole in the middle, flanked by fighters, for example.
By the way, Empire of the Petal Throne conforms to this approach. In EPT three abreast in a 10' corridor is standard, with three exceptions. If a character is using a two-handed weapon only two will fit. If that weapon is a two-handed sword only one character has room to operate in that rank. And wimps like spellcasters can actually squeeze in four abreast in 10'. Small characters like halflings probably also fall into that category.