I’m pretty sure they’ve been profitable since the first month of private repos.

AFAIK the timeline of profitability is somewhat like this:

- really profitable after introducing private repos - burning quite some money for growth after they took VC money - really profitable again after they changed their pricing to per-seat pricing

They lost 66 million as recently as 2016.

https://news.ycombinator.com/item?id=13188574

They introduced the new pricing in the middle of 2016[0].

[0]: https://blog.github.com/2016-05-11-introducing-unlimited-pri...

Most companies leave startup status long before they are profitable. It has much more to do with the stability and maturity of the business model and whether it can be scaled.