I can tell you that graph is full of shit because you can go back through recorded incidents here

https://www.githubstatus.com/history

And immediately find that there are numerous incidents that would show up on the modern status board as an issue but are reported with 100.00000% uptime on that graph.

One example:

https://www.githubstatus.com/incidents/bzj1hc2cnfkc

2018-07-16 17:32:53 - We are investigating reports of elevated error rates.

2018-07-16 17:34:27 - We are investigating reports of service unavailability.

2018-07-16 18:04:38 - We've discovered the issue causing connectivity failures and are remediating.

2018-07-16 18:26:48 - We're monitoring the site as systems recover. Some delays are expected as we process backlogged data.

2018-07-16 18:37:26 - We're continuing to monitor and work on further remediation efforts as the site recovers.

2018-07-16 18:54:21 - The site is stable. We are continuing to monitor and work through follow-up remediation efforts.

And there are other incidents with connection failures or elevated error rates during July 2018, but the linked graph shows "average uptime of all components 100.00000%" during July 2018.

Another from October (that also shows 100.0000% uptime)

2018-10-21 23:09:19 - We are investigating reports of elevated error rates.

2018-10-21 23:13:31 - We are investigating reports of service unavailability.

2018-10-21 23:43:55 - We're investigating problems accessing GitHub.com.

2018-10-22 00:05:37 - We're failing over a data storage system in order to restore access to GitHub.com.

2018-10-22 00:23:54 - We're continuing to work on migrating a data storage system in order to restore access to GitHub.com.

2018-10-22 00:43:12 - We continue to work on migrating a data storage system in order to restore access to GitHub.com.

2018-10-22 01:02:49 - We continue to migrate a data storage system in order to restore full access to GitHub.com.

2018-10-22 01:22:22 - We continue to work to migrate a data storage system in order to restore access to GitHub.com.

2018-10-22 01:41:19 - We are continuing to work to migrate a data storage system in order to restore access to GitHub.com.

>I’ve been using github pretty much daily since 2010 and I never had a push fail or a repo be unavailable until recently.

Looking back at their downtime history. Unless recently is within the last 3 years, it seems like you got really lucky.