As open-source as possible means that certain elements of it will be kept a secret.
Open source hardware definition is clear, they are transparent and there is no some ''secret elements'' in them, oh and you are quoting some old blog post from 2020, and new information I heard confirmed what I am saying, but let's wait the end of 2022 and see, if we are alive by them.
You can't change a license just a little bit, add common clause and still call it open source like Coldcard wallet is doing with their device.
"Open hardware," or "open source hardware," refers to the design specifications of a physical object which are licensed in such a way that said object can be studied, modified, created, and distributed by anyone.
https://opensource.com/resources/what-open-hardware