It's hard to tell what, exactly, the position on "open source AI" was. It's presented here in glittering generalities. Given the many conversations I've had on-theme with not-public-tech-co people, I don't think it's fair to say all of "little tech" has one view or position, when you really get down to details. I rather doubt the whole YC-o-Verse sees it all one way, either, given its burgeoning size.
More broadly, I'd expect positioning off as "little tech" to flop. Policy players know how to follow the money. They know "Big Tech" brings the money that buys startups—they've read about it in exec summaries of the committee reports. They're also plenty aware that startups get founded by, and recruit from, a lot of the same pools of people. They've been lobbied by various policy groups speaking for smaller tech companies, often funded by the bigger tech companies, for years. If they dig just a little bit, they'll see the barriers to entry, and resulting big-co dependencies, for small-cos doing AI work.
There's bipartisan support for "going after Big Tech" competition-wise. I don't think the pols need a tech-co splinter group as reinforcement there. Unless and until IPO becomes the main path of successful ascent again—perpetually private isn't popular—I don't have great arguments against generalizing startups to Big Tech Farm League. There are plenty of gripes up from startups against the Great Houses, especially from investors. But that's feudalism for you.
Compare, say, DHH's lobbying. 37signals had the Bezos investment, but it was an unusual deal, not within the usual system. Speaking from a different place.