Steps to reproduce:
Create Agent 2 check with 1 h update interval (no matter the value, just not frequently checked), reboot the server, get no data, for example, about uptime change.
If item collected with 1m or 5m - you will get updated values, but with less frequent updates you will get "blind" for the update interval of the item if Agent restarted.
Documentation has no information about difference with Agent 1:
Difference should be mentioned in the documentation.