Agreed, and I can find no roadmap for it. It's a real shame.

I'm looking at moving to something a bit more application aware now, such as Traefik, which works better in my workflow anyway.

Will say though - HAProxy has been rock solid for me, and was a million times easier to configure and manage than F5 LTM for our use case.

I wonder if that's because it may have to decode all the data going over the pipe to figure out where headers are? As it stands HAProxy only looks at and modifies HTTP headers and passes the body right on through without touching or modifying it.