POE from Cisco Switch To hAP ac

Hello All.
Maybe it is strange to ask question about something, which is working properly .But on the other hand I am curious why.
I use CISCO SG300-28P as main home switch and 2 hAP ac as APs. Originally both hAP ac were powered by power adapters, but by luck I detected that they can also work with POE from the switch. This is a litle bit surprising as CISCO should support IEEE 802.3af standard only and hAP ac can be powered only via Passive PoE. It does not work on all switch ports and it can takes few minutes to MT to boot. By if it works, it works reliably.
Any reasonable explanation or similar experience?
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