https://www.zabbix.com/documentation/3.0/manual/web_interface/frontend_sections/configuration/hosts/items and https://www.zabbix.com/documentation/3.0/manual/web_interface/frontend_sections/configuration/hosts/web say :

• Clear history - delete history data for items
• Clear history - clear all history data gathered so far on the scenarios

a) these also delete trend data;
b) i'd suggest to unify these sentences, maybe even just "delete history and trend data" for both ?

should be done for all versions (as applicable, for web scenarios clearing was added in 2.4 only, ZBX-7979)