Employees shouldn’t be using the corporate network to view porn. Everyone nowadays (especially Meta employees) has smartphones with personal hotspot capability. Just use that if you really need access to such content in the office.
In fact I don’t really buy their reasoning - surely everyone working as a software engineer knows that SNIs are unencrypted and any corporate network will log them, so nobody should be accessing any kind of objectionable content via the corporate network for their own good to avoid embarrassment.
So I suspect the porn access may have been due to an actual AI scraper (not arguing that they trained on porn - it could very well be there are 2 stages - one is a basic scraper more or less following links, including accidentally following a pornographic link posted on a non-porn site, and another stage classifies the content and the decides whether it should be used for training or discarded).
If this was actually employees accessing or torrenting pornographic content, I’d expect this to be quickly followed up on and the employee facing dismissal after a stern warning (or an IT security investigation if they persevere in claiming they didn’t do it, as it could suggest malware using their machine to proxy traffic).