It is explained in other article in the same website.
The problem is that Debian endorses NonFree software by hosting it in the repositories and providing certain guides.
There are no “blobs” or nonfree software in the main repository and normal installation (you can enable these nonfree repositories manually or using an expert install).
I believe PureOS went out of its way to remove any proprietary blobs from the stock Debian codebase.
It is explained in other article in the same website.
The problem is that Debian endorses NonFree software by hosting it in the repositories and providing certain guides.
There are no “blobs” or nonfree software in the main repository and normal installation (you can enable these nonfree repositories manually or using an expert install).
A Debian installation is fully free.
I stand corrected then!