Not true at all; someone with the brains to understand how software works at the lowest level can figure out the higher levels easily, while the reverse apparently doesn't hold.
I've worked with enough backend developers who complain on how much tooling there is in frontend to know that this isn't true. And being a "fullstack developer" myself I've seen the stuff that sysadmins deal with and I know that thats a job I could never do. Knowing one part of the stack doesn't automatically qualify you for the other parts. Knowing assembly doesn't make you an expert in CSS, Webpack nor configuring IIS servers.
