Currently, Web monitoring only save 3 metrics:

• HTTP response code
• Response time (total_time curl information)
• Download speed

Curl is also able to give much more detailled informations, for example:

• CURLINFO_NAMELOOKUP_TIME
• CURLINFO_CONNECT_TIME
• CURLINFO_APPCONNECT_TIME
• CURLINFO_PRETRANSFER_TIME
• CURLINFO_STARTTRANSFER_TIME
• CURLINFO_REDIRECT_TIME

Zabbix should be able to store them as well so that one can investigate a strange scenario behaviour.
This will also relevant for those who want to do some performance monitoring.

My company might consider sponsoring this feature's development. Just need to have an estimation of the dev complexity and impact on Zabbix server side as well as database.