Sticking two E2EE tunnels together with a plaintext middleman doesn't result in a single E2EE tunnel.

The reason the distinction is important is because the security profile is vastly different—a compromised server leads to a compromised message—which isn't true for actual E2EE services like a pure Matrix link.

Side note: the first thing you should ask of a "end-to-end encrypted" product to you is "which 'ends' do you mean?" I've seen TLS advertised as E2EE before.