I know that, that's why I wrote better in HTTP/2, but you still need to transfer more data. no matter how it's compressed you still have data. while on the other side you have not. actually in your cloudflare blog post you also see that they save up to 15%. well meaning the more files you send the better it gets, but you never can eliminate it. keep also in mind that for every "SETTINGS_MAX_CONCURRENT_STREAMS" size the HPACK compression might be equal.

also many small files means that you not just send more header frames, also the whole chatty http/2 protocol sends more data. http/2 is chatty and stateful, that's something people should know about. so the best possible outcome is probably do concat, but don't be so aggressive than on http/1 do concat more when you have more mobile users since http/2 does not fix their mean latency and their bad bandwidth