I think you're referring to this tweet:
https://twitter.com/eastdakota/status/1506148082194386949
I believe @eastdakota is saying that Cloudflare has their own homegrown SSO internally, but they do not make that available externally to their customers (it's not a public product that one can buy). I don't think that the tweet was saying that they use Okta externally.
Anyway, I likely misinterpreted yesterday’s comment..