According to https://tools.ietf.org/html/rfc2068#section-19.7.1.1 HTTP/1.1 defines the "Keep-Alive" header for use with keep-alive parameters but does not actually define any keep-alive parameters. I don't see a definition of this header in any of the RFCs that obsolete this one (just some mentions of issues with persistent connections and HTTP/1.0 servers, and the fact that Keep-Alive is a hop-by-hop header).

MDN's documentation on this header references https://tools.ietf.org/id/draft-thomson-hybi-http-timeout-01... for the parameters, but this is an experimental draft that expired in 2012.

Which is to say, I can't really fault Safari for not respecting keep-alive parameters that never made it out of the experimental draft phase.

You and eridius are talking about the Keep-Alive: header. The article at hand appears to be talking about the Connection: header.