I suspect that doing a full swivel would have added quite a bit to the complexity
Actually just disconnecting the rear foot from the screen would remove complexity but then you couldn't sell it as a pretend Psion.
The fact is that this is just a smart phone in a fancy box, running something other than android would have made the difference but since the hardware was orginally for the mobile market then you have to do your own linux which is where the difference between the RPi and this or say pine64 comes.
Now you can buy a laptop style case with 14" display/keyboard etc for the RPi and use a decent fully working/supported linux and for much less money although admittedly with correspondingly less CPU. This being because the RPi design phylosophy put more emphasis upon linux than a fancy box and have gone out of their way to keep android off the RPi.
Thus I would say that if you want a portable keyboard with a maintained linux for say remote shell/RDP etc then the price of the added CPUs is for no benefit at all and having also kept my libretto 50 (still working on battery) I can say that remote working on a tiny screen didn't help with the aging of my eyes, the 14" one for the RPi is much more functional and people won't accuse you of excessive self abuse.
However if you want a smart phone that says "I am a sysadmin, bow before my Psion style packaging" but doesnt come with a fully accessible linux then clearly you put useless pretties above functionality or perhaps you just want an advertising discount.
As an asside I still have my Acorn Pocket book 2 (Psion3) and it works today just as well as it did when I bought it i.e for weeks on full batteries, show me the smartphone that is still secure, fully working and has not needed any repair for a fraction of that working life and I will agree that it is Psion like.