GitHub probably _had_ deep levels of performance expertise, but getting acquired by a megacorporation comes with a big shift in culture. I’d bet that many tenured GitHubbers left, and that there are relatively few people remaining who understand the core systems deeply.

Medium-term, the more closely aligned with the rest of Microsoft’s technology they can become, the better - not many MSFT folks understand the ins and outs of sharded Percona, but many of them do understand SQL Server and .NET.