If you do the math (also a common system design interview question for an AI lab), its actually only ~3PB (compress to 1PB, ~$22,000/mo in S3) and a few thousand/mo in compute over less than 4 months to index the entire internet for pretraining purposes. At that price point, its actually very affordable to many thousands of organizations to get their own copy. I would expect the major labs to special case kernel.org similarly to other sites like Wikipedia, but not the majority of scrapers

There are many more labs than that, and humans aren't designing unique scraping processes per domain.