Hello, EVA AIR. Thanks for your message.
I tried booking from HKG to SFO and from HKG to NRT.
(two different itineraries). Both were H-class. (the special
promotion via web booking) But I couldn't do.

I checked Amx website to check the availability in advance
of web booking, and I confirmed H-class was available for
booking, then tried. But I couldn't. And the staff confirmed
H class was available when I contacted them. Amazing the
staff said to me,

"H class in our booking system in our office is
different from H class which can be booked via the
web site."

How many H classes do they have??