I'm constantly fascinated by the novel rules detail in OD&D Swords & Spells. There's a bunch of stuff in there that can be interpreted as updates or clarifications to the core D&D rules -- stuff that often failed to matriculate forward into later versions of the game. Ironically, it's the only little-brown-book I had as a kid, until I got a copy of the other stuff well past 2000 A.D.
Here's one: Recall that in the OD&D LBBs (1974) all hit dice and damage were just d6's by default. Then Supplement-I (1975) changed that to give different hit dice by character class, d8's for monsters, assorted dice for weapons, and a kaleidoscope of increased and altered attacks and damage for all the monsters in the game (e.g., ogre damage goes go from 1d6+2 to 1d10, hill giants go from 2d6 to 2d8, etc., among many other variations). We get linking text between those pieces like the following:
If varying amounts of damage according to weapon type used is employed, the various monsters will likewise be subject to-receive additional points of damage or dice of damage.
And:
This [elaborated damage for monsters] system is to be used with the varying damage by weapons and in no event is it recommended for use without the aforementioned.
But in Swords & Spells (1976) we get an unexpected combination (from p. 17):
The amount of damage base (1-3, 1-6, etc.) is a function of the size of the attacker and/or weapon size. As a rule of thumb, small creatures will do 1-3 base damage (exception: dwarves). Those large creatures indicated in the D&D rules as doing above-average damage (ogres 3-8, giants 2-12) will use the appropriate base. Once the appropriate base damage is determined, simply cross index the level of attacker against the armor class of the defender to find the number of hit points of damage scored upon the defender. Thereafter, modify this number by any bonuses or penalties to determine the final number of hit points of damage inflicted.
The amount of damage various creature types can sustain is computed by multiplying the average number of hit points a single such creature can sustain by ten (the number of scale creatures represented by a single figure) times the number of such figures mounted on a single stand. Mounted troops include the hit points of their mounts. For example, assume a stand of 10 orcs: the average damage an orc can take is 1 die or an average of 4.5 × 10 = 45 × 10 = 450 points, with a figure removed at 45 points, and a scale orc killed for every 4.5 points of damage inflicted on the unit.
While the signal we get in Sup-I is that the updated hit dice and damage are meant to be taken as a single package, in Swords & Spells, Gygax's monsters are using the updated hit dice (d8, for 4.5 points average), while still using the original uninflated damage (with the tweak that small monsters get only 1d3). All the recognized monster damage is still some multiple of d6 dice. The core combat tables reflect this: the only options presented for monster damage are 1d3, 1d6, 1d6+2, and 2d6. (Meanwhile, "Human-type" combat tables support damage in ranges 1d3, 1d6, 1d8, or 1d12.) There's also a table of damage for mounts (p. 18), on the same base d6 scale, with output much reduced from the earlier Sup-I revision (in particular: just a single attack each, instead of the claw/claw/bite routine set out for most in Sup-I).
It's an interesting editorial choice and I kind of like it. Without having noticed it before, it mostly lines up with I decided for monster damage in the OED Monster Database, reflecting an interpretation of late-era OD&D, but one where monster damage is kept on on the 1d6 base scale. For a long time I've been fond of the DM running everything with a pile of d6's behind the screen, while the PCs get to experience a finer-grained experience with the other polyhedral dice on their side. And my intuition is likewise to drop small-creature damage to 1d3.
Did you ever think to be surprised by this representation in OD&D Swords & Spells?