Eh, I think Linux Hater is overstating it, and his choice of LAMP as an example of a "get it right" stack is ironic, given that it's the M in LAMP that we're criticizing here.
I think having lots of choices works fine in many contexts. It's just that, in this case, a DBMS's storage engine is something that needs to work well in many cases, and having choices is harmful to that goal.
PostgreSQL offers many choices, in other contexts: you can add your own types and operators, extension packages, and even procedural language handlers, so that you can write database functions in the language of your choice. The difference here is that the choices are built on top of a solid foundation in which the basics "just work".