The USGA are all from the Professional / Managerial class so they choose to govern incrementally, like the Democratic party.
Limiting the length of the shaft was seen as easy because it does not directly threaten any manufacturer's market share -- nobody is the leader in 48-inch drivers right now. But Callaway is still going to push back, because they are a corporate entity who thinks nobody should regulate them at all, and they don't want to set any kind of precedent.
The only surprising part of the discussion to me is that Jeff is in favor of allowing players to use their "skill" to hit a 48-inch driver, even though he's usually in favor of limiting distance. Nobody was using a 48-inch driver with a persimmon head; they might have whiffed. Since they're governing like Democrats, though, maybe they will means-test driver length and let taller players use a longer driver? Or is it shorter players that need it to compensate? I'm not clear.
So, this is weenie governance, but who expected more in 2021?
I like to keep 'em guessing.
As you point out, very, very few were using a 48 inch driver with persimmon and steel(the same as now quite frankly), though Rocky Thomson used a 52 inch driver quite well.
My point has been that the ball(multilayer), face that caves in and rebounds are the low hanging fruit, and what has changed the most in distance gains.
Shaft lightness and length are huge factors too(steel shafted drivers used to be 43-43.5 inches long-mine was 44-now they are generally 45 sometimes 46) , but changing the shaft weight affects lots more than elite players, and especially the weaker, older or female player.
I'm just saying there IS a tradeoff when one wields a 48 inch driver or more, and wielding it well is a skill.
By going after that, they've taken that weapon from an LPGA player, and done NOTHING to a PGA Tour player, and once again have dodged the issue almost completely, other than Michelson...
So I'm against yet another half measure that does nothing, as it distracts form what I believe is a real issue-the scale of how far the ball goes and how big the courses tend to get as a reaction-to say nothing of the long and wrong factor with young wild drivers and the fact nearly all driving ranges are becoming irons only for anyone with any speed at all.