hEX S product page specifies passive PoE out of up to 57V. But won't regulate voltage, PoE out voltage is the same as power input, supplied power brick is 24V 1.2A.
wAP ac product page indeed says 802.3af/at PoE in, but also specifies PoE in voltage 11-57V. Knowing that 802.3af/at voltage starts at 40+V and is nominally 48V, one can guess that wAP ac also works as passive PoE PD. And indeed all of current Mikrotik devices that support PoE in are capable of passive PoE in, only select devices are capable of 802.3af/at PoE in.
Brochure for wAP ac (available from product page) indeed explains different powering options in a bit more detail:
PoE in Yes
Supported input voltage 11 V - 57 V (802.3af/at with shielding not connected to GND pins, passive PoE)
So in short: wAP ac will happily run off hEX S PoE out port.