SingleStore is a kind of uninteresting example because it is not open-source. It makes potential customers feel non-confident. Why move large data volumes to SingleStore if the company can cease to exist in a year?
Yep, SingleStoreDB (formerly MemSQL) is not open source (probably never will be), but it does have many paying customers who have had workloads in production for over a decade at this point.
Also, isn't taking a bet on a very recently launched database as a service based around an open source database also pretty risky? Say for example the very recently launched Clickhouse Inc. service (which your a co-founder of?).