Nothing. You don't even need the LLC. I don't think anyone got prosecuted for only downloading. All prosecutions were for distribution. Note that if you're torrenting, even if you stop the moment it's finished (and thus never goes to "seeding"), you're still uploading, and would count as distribution for the purposes of copyright law.
>Meta allegedly tried to conceal the seeding by not using Facebook servers while downloading the dataset to "avoid" the "risk" of anyone "tracing back the seeder/downloader" from Facebook servers
Sounds like they used a VPN, set the upload speed to 1kb/s and stopped after the download is done. If the average Joe copied that setup there's 0% chance he'd get sued, so I don't really see a double standard here. If anything, Meta might get additional scrutiny because they're big enough of a target that rights holders will go through the effort of suing them.
Citation needed. RIAA used to just watch torrents and sent cease and desists to everyone who connected, whether for a minute or for months. It was very much a dragnet, and I highly doubt there was any nuance of "but Your Honor, I only seeded 1MB back so it's all good".