For spell areas of effect, inches are always tens of feet. It is only spell ranges that increase to yards.
In 2nd ed AD&D they got rid of this notation, and just gave spell ranges in yards (thereby giving all spells much longer range indoors/underground).
But if you read the actual text of the spell, it specifies the volume as "33000 cubic feet, (or yards)", so this particular spell's area does increase outdoors. And in 2e they clarified that the spell will fill 33 10x10x10 cubes, while keeping the "or yards" notation. It's there in 1e, but less clearly stated.
In 3e the authors made it clear that the specific always overrides the general. For earlier editions we have to use some brains and actually read the spell text, instead of just the header.
And since we're using the Wayback Machine, the 1e spell
Transmute Rock to Mud listed it's area as 2" cube per level. There was some debate if this was one 2" cube per level, or a single cube that was 2" on a side per level. For a 10th level caster, this was the difference between 80,000 cubic feet of stone and 8,000,000 cubic feet of stone. We referred to this spell as "Slay Castle".

(Admitted, the 8,000,000 interpretation required selective reading.)
And, to add to the glee, the Sage said the volume was two 1" cubes per level, the volume that was eventually listed in 3.0 and 3.5. How anyone would read '2" cube per level' and get '2 1" cubes per level' is beyond me.