Great observations around how popular and useful it is for systems to have some level of Postgres line compatibility! Thanks for doing the writeup!
One thing that's not totally clear in the comparison table is that most of these implementations are just that, databases providing an abstraction through the Postgres wire protocol over a different database architecture/parser & solution.
TimescaleDB, however, is the only one listed that is built directly on Postgres as an extension. There is no abstraction layer over some other implementation of the query parser or storage layer.
When it comes to application maintenance and developer expectations at query time, not all of these are apples-to-apples comparisons, as some of the other comments have noted.