with lts and non-lts branches, there are likely to be more users who will skip some (non-lts, likely) branches. when reading the upgrade notes in the manual, they might read only the lts, missing the intermediate non-lts upgrade notes.
for example, upgrading to 3.0 from 2.2, they will miss the 2.4 upgrade notes.

it is suggested to link to 2.4 notes in the 3.0 page https://www.zabbix.com/documentation/3.0/manual/installation/upgrade_notes_300 - a large note saying something like "if you are upgrading from 2.2, make sure to read [2.4 upgrade notes, too]" ( [ ] denoting a link)