C++ can be written to be safe. I don’t think WH is the right authority to issue this warning. Naming C++ rather than going after specific features is unfair.
I suspect that the white house just received a report from some people in the industry stating that faulty software is vulnerable to attacks from bad actors, and from that basis they just went the simplistic path of arguing that 1) lots of software is written in C++, 2) that software has bugs, therefore if we don't use C++ then we won't have bugs.
As a branch of government, their role is not to evaluate technical merits of proposals but to hear what their representatives have to say.
I think this can be explained by underlining the differences between could, would, and should.
The blog states the fact that at least some C compilers already offer the necessary and sufficient tools that characterize "memory-safe" languages, and proceeds to illustrate examples. This isn't new. However, just like "memory-safe" languages enforce narrow coding styles through a happy path that is expected to prevent the introduction of some classes of vulnerabilities, leveraging these compiler features in C projects also requires the same type of approach.
This isn't new or unheard of. Some C++ frameworks are also known for supporting their own memory management and object ownership strategies, but you need to voluntarily adhere to them.