I seem to recall reading that, but I think you have the wrong impression. I’m pretty sure it’s just there build system. They have always had two (one private for the paid stuff), and now they are just building everything “in private” not removing any source.

There are many projects that do not have open build systems, and I can understand them eanting to cut costs and simplify infrastructure.

e.g. just because redhat has a private build system and tries to restrict access to their binaries, that does not make them closed-source.