This post here is the demonstration, that some non-WebPKI purpose is causing issues and complaints. This has happened before with SHA-1 deprecation. WebPKI does not want this burden and should not have this burden.

Ok, so this is an official split of "WebPKI" and "everything else PKI" then?

Last time I checked, Let's Encrypt was saying they provide free TLS certs, not free WebPKI certs. When did that change?

That's being overly pedantic. PKIs for different purposes have been separate for a while, if not from the start. LE is still giving you a "TLS cert".