Their intention for specifications are clearly stated in the earlier part of the document:
Thread Group [...] grants you [...] license [...] to view, download, save, reproduce and use the Specification solely for your own internal purposes
[...] you shall not: 1) loan, rent, lease, sublicense, sell, or permit others to use the Specification; 2) modify, adapt, translate, or otherwise change the Specification in any manner or create any derivative work of the Specification;
[...] copy or reproduce the Specification except for backup or archival purposes in connection with your internal use; or 4) remove any proprietary notices or labels on the Specification.
So yeah, you can't create derivative works from these specifications. Is a blog post about it a derivative work? Who knows. Probably not. Probably what they meant is you just can't create your own Threads 2.0 specification or create unauthorized translation of it (which although restrictive is reasonable because they just don't trust you to not mess things up). They clearly just want to remain the single source of truth for Thread specification on the net, to avoid ecosystem fragmentation and they intend to sustain themselves from licensing fees from commercial device manufacturers.
Even with all their conditions normal rights to citation, critique, parody probably apply.
Thread Group [...] grants you [...] license [...] to view, download, save, reproduce and use the Specification solely for your own internal purposes
[...] you shall not: 1) loan, rent, lease, sublicense, sell, or permit others to use the Specification; 2) modify, adapt, translate, or otherwise change the Specification in any manner or create any derivative work of the Specification;
[...] copy or reproduce the Specification except for backup or archival purposes in connection with your internal use; or 4) remove any proprietary notices or labels on the Specification.
So yeah, you can't create derivative works from these specifications. Is a blog post about it a derivative work? Who knows. Probably not. Probably what they meant is you just can't create your own Threads 2.0 specification or create unauthorized translation of it (which although restrictive is reasonable because they just don't trust you to not mess things up). They clearly just want to remain the single source of truth for Thread specification on the net, to avoid ecosystem fragmentation and they intend to sustain themselves from licensing fees from commercial device manufacturers.
Even with all their conditions normal rights to citation, critique, parody probably apply.