According to Zabbix docs - orange wrench icon "indicates that this host is in maintenance". The semantics of what "in maintenance" means is not uncovered.

Originally, when Maintenance covered only Host Groups and Hosts, the semantics was clear - the marked entity (host) is likely to have some suppressions applied. With the introduction maintenance with filtering by Tags and Event Names, the semantics get blurred, and may be confusing.:

AS-IS:
GIVEN maintenance is applied to Host Group = groupA AND Tag = a contains 'a'
THEN maintenance indicator is shown for the Host Group groupA,
AND maintenance indicator is shown for all Hosts within the Host Group groupA

If the "In Maintenance" indicator semantics mean: We highlight the whole hierarchy of objects starting with the selected root, that there is likely some work is happening - the behavior is OK

If the "In Maintenance" indicator semantics mean: We want to highlight only exact entities affected by the maintenance (t.i. have suppressions), then:

EXPECTED
GIVEN maintenance is applied to Host Group = groupA AND Tag = a contains 'a'
THEN maintenance indicator is shown for the Host Group groupA,
AND maintenance indicator is shown for Hosts and Triggers that has Tag a:a