The way I'm reading the sections you've quoted, the spec merely allows proxying of https ciphertext. Every router in the internet does that already. Bear in mind that in HTTP 2.0, all connections are TLS connections. The spec sections you've quoted just say that users should only have to consent once to their "http"-resource connections being proxied; they're not talking about "https" resources.
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The way I'm reading the sections you've quoted, the spec merely allows proxying of https ciphertext. Every router in the internet does that already. Bear in mind that in HTTP 2.0, all connections are TLS connections. The spec sections you've quoted just say that users should only have to consent once to their "http"-resource connections being proxied; they're not talking about "https" resources.