I'd consider staff in those areas core to the product. Many of the dozens of projects at https://opensource.twitter.dev/projects/, not so much. Staff whose job revolves around standing at booths at conferences and handing out swag, ditto.

How many of those are active? How many of those were created for the purposes of twitter infrastructure and released as a side effect?

I'm sure that you can stop supporting the open source section. However, how much of their platform team is core to the product? How much is still required?

I'm sure many of those projects are out of date. Either way, they could probably make them all private for their purposes and stop accepting PRs (probably just turn them lose on the greater OSS community for those that still rely on them)

Imagine going to jail because someone uploaded a file to your computer

Which, by the way, is exactly what "Section 230" prevents.

Child porn is explicitly carved out from the section 230 immunity.