As far as I remember having a predefined default was never actually considered.
I don't know what the default is now, but the intention was always to make it the default:
Whoever wrote that blog post made several claims which are contradicted by the linked blog post. I'm wondering whether that's just being confused on the different between enabling the DoH code behind a disabled default setting and changing the default configuration to use a particular server.
Here's what Mozilla said:
> Firefox does not yet use DoH by default. See the end of this post for instructions on how you can configure Nightly to use (or not use) any DoH server.
> Our second effort focuses on building a default configuration for DoH servers that puts privacy first.
https://blog.nightly.mozilla.org/2018/06/01/improving-dns-pr...
But being the default? That’s just crazy.