Yes - each pocket has a valve: the valves & their "cylinder heads" are identical. Obviously the inlets face into the cylinder block & the outlets face out to the high pressure head. The pic is of the inlet head, but confusingly I just popped two valves into it the wrong way, to save losing them!( they hold in OK). That configuration is the same as the outlet head, except with a pressure connection.
I must admit it looks like an O ring setup but perhaps, as you suggest ,it just needs better O rings than I have at hand...