SpaSitePipeline should not include preamble or epilogue comments in the response

I think in an SPA setup, always the SPA should be responsible for adding the "PAGE-META-DATA", since the SPA can also be a server-side rendered SPA where the SPA is proxied into the CMS site preview : Then of course, the SPA must provide the PAGE-META-DATA.
Now, given that the SPA must inject the PAGE-META-DATA, it is now quite odd that the HST in case of the SpaSitePipeline already includes the PAGE-META-DATA already in the HTML (in case the SPA is rendered by the HST thus). Even more confusing is, that the targeting PAGE-META-DATA is not included since the SpaSitePipeline does not have the targeting valve.
Hence, I am quite sure that the SpaSitePipeline should not render any preamble or epilogue comments : These should always be injected by the SPA.