The author pretty clearly states why they used the form factor:
it’s my take on the slab style computers that were somewhat popular before the world settled on clamshell designs for portable computers. I really wanted a TRS-80 model 100 when I was young so this sort of design was a big influence.
not everything is built for everyone, and that’s cool & fun
hell ya for being able to buy these used as office surplus in 5 or so years