I would say this statement is a very clever move from GitHub side. I guess they have skilled PR people working on the issue.
At first look, the cited article seems to admit to everything. As a result, it will be sort of last news on the topic - if they admitted Horvath is right and they even put on leave a founder and the programmer and founder's wife will not be allowed to enter office, then what's more can be said or written? Github did everything it could to resolve the issue.
The point is that they did not admitted anything. The only paragraph that contains actual content is paragraph no 2., the rest is just speaking how Github grows and how they liked Horvath, how sad it is that Horvath is sad, etc.
So we have:
"We know we have to take action and have begun a full investigation. While that’s ongoing, and effective immediately, the relevant founder has been put on leave, as has the referenced GitHub engineer. The founder’s wife discussed in the media reports has never had hiring or firing power at GitHub and will no longer be permitted in the office."
So they have started "full investigation", just that. After two months when everybody will forget about the issue, the founder with his wife and the programmer might be back at Github (who knows what the investigation is going to prove - Horvath will not take part in it - she's no longer an employee). Whatever happens nobody will pay attention. No media will investigate the issue further because "Github admitted Horvath is right", so the topis is closed and no longer "hot".
I guess GitHub cannot publicly admit that Horvath is right or not, their lawyers would be mad, it is much better for them to keep all statements fuzzy and sounding good.