This is also how I justify my opinion that the "no independent implementations" was more of an afterthought excuse, and less of a primary motivation on Mozilla's part.
(I'm a little pressed on time here, but I could probably find more examples if I had more time to search... Sorry!)
Quoting Jonas Sicking from a W3C IRC log[0]:
> we've talked to a lot of developers
...
> the feedback we got is that we really don't want SQL
Quoting Maciej Stachowiak from the "public-webapps@w3.org" list[1]:
> Hixie has said before he's willing to fully spec the SQL dialect used by Web Database. But since Mozilla categorically refuses to implement the spec (apparently regardless of whether the SQL dialect is specified),
...
> At the face-to-face, Mozilla representatives said that most if not all of the developers they spoke to said they wanted "anything but SQL" in a storage solution.
The comments relating to JOIN in the comments on Mozilla's blog post comparing IndexedDB and WebSQL[2] betray the anti-SQL (and, arguably, anti-relational database) stance at Mozilla.
Mozilla's people didn't like SQL, so any excuse for dismissing WebSQL (or even a simplified SQL dialect that didn't have the "quirks" of SQLite) was a foregone conclusion.
And now here we are shipping >1MB transpiled WASM payloads around when we could have agreed on a query language feature set implemented in native code using a consistent back-end standard storage format.
[0] https://www.w3.org/2009/11/02-webapps-irc
[1] https://lists.w3.org/Archives/Public/public-webapps/2009OctD...
[2] https://hacks.mozilla.org/2010/06/comparing-indexeddb-and-we...