a but that has piece that reach up or down the face or both is called a fulmer (or full cheek) this bit is used for directional help and has no poll pressure.
A full cheek has eggbutt rings fixed to the cheek pieces. A true fulmer has the reins attached to loose rings which are attached to the cheks by short links.actually the full cheek and the fulmer are the same thing. i think you will find this is stated in any bit book and i even had a look on the link you posted and it's the same there too.
as for poll pressure, i'm sure if you speak to heather from neue schule she will set you straight about her bits and exactly what they do. as she designed the bits to do certain things i think she is the best expert to ask about it. if the bit is used correctly it does have a poll action, and i should know i've tested it many times as it's one of my best selling bits.
i must also point out that my stallion reacts to one exactly the same way as a hackamore
claire. the purpose is to stop the bit crushing the tongue against the bars of the mouth. it does still act on the bars to an extent, just differently to other snaffles. it's often the case with single links and plates that they break in the wrong place and this squashs the poor tongue and make the horse put the head up to get the tongue free. you will also find that horses will snatch the rein to do the same thing. they also can't swallow if the tongue is pinned which some bits do.