There a few claims you have that I think are slightly off.
First, push is very different than inlining, because individual resources are cacheable by the client, and inlined resources are not. There's a little handshake at the start of a push and if the client has (or doesn't otherwise want) the resource, it can cancel the push.
In my team's experiments with using push for HTML Imports, push ends up being better than inlining (using Polymer's vulcanize tool), even with a cold cache.
Also, push is relatively easy to implement if you use the response header approach, and was availably early on in mod_spdy.
First, push is very different than inlining, because individual resources are cacheable by the client, and inlined resources are not. There's a little handshake at the start of a push and if the client has (or doesn't otherwise want) the resource, it can cancel the push.
In my team's experiments with using push for HTML Imports, push ends up being better than inlining (using Polymer's vulcanize tool), even with a cold cache.
Also, push is relatively easy to implement if you use the response header approach, and was availably early on in mod_spdy.