Well, it means all your handling of messages is the same — once you have built your object/struct/whatever of the message (from the over-the-wire syntax), you c

Well, it means all your handling of messages is the same — once you have built your object/struct/whatever of the message (from the over-the-wire syntax), you can hand it off to pre-existing code that expects HTTP/1 messages fine. Most HTTP/2 implementations share a fair bit of code with co-existing HTTP/1 ones. You don't need to redo all your caching support and handling of HTTP caching headers, you don't need to redo any support for content negotiation you have, etc.