As usual, Gygax's Swords & Spells book (which counts as being in the OD&D line) gives some nice additional perspective if you hunt around in it enough. In these 1:10 mass-combat rules, catapults are explicitly said to be 1:1 scale, which I think bolsters my previous argument:
Artillery: As the various artillery pieces represent but a single scale engine, only a single figure is needed to represent crew for each... [S&S, p. 10]Catapults (both light & heavy) have decreased rate-of-fire from 1/2 or 1/3 [CM, p. 12] to 1/4 here [S&S, p. 9]. Meanwhile, bow archery has increased rate-of-fire from 2 per turn [CM, p. 11] to 3 per turn [S&S, p. 9]. And as far as giants go:
Giants act as 20" range -- light catapults with a fire arc of 45% [sic] left or right, but they must stand one-half move to fire. [S&S, p. 10]That's an oddball rate-of-fire: sort of between the allowances for ROF 1 or 2 [S&S, p. 9], now much more potent than a mundane light catapult (by a factor of 4), similar to the description in Chainmail but without following the Swords & Spells reduction to catapult speed. This is backed up by the Example of Game Play at the back of the book which features giants throwing rocks on each of subsequent turns [S&S, p. 38].
Now, the thing I thought particularly interesting is that the result of catapult/giant fire is already no longer an area-of-effect. And I think this is particularly reasonable if we're interfacing between scale 1:1 throwers and 1:10 targets. The effect is now simply an application of a certain number of hit points damage to the target unit [S&S, p. 26]:
|STONE CASTERS||Target About Man-sized||Larger|