They were supposed to. This company was launched on an ill-fated Kickstarter for a slide-out keyboard attachment called "Livermorium" for the Moto Z. It's the reason I owned a Moto Z.
I have no interest in buying a no-name brand phone, though.
Problem is, Motorola took its time certifying the keyboard and by the time they were done, hardware components where no longer available, so they had to redesign. Same thing happened again, but they successfully delivered a few prototypes. After which Motorola discontinued the attachment ports altogether.
So fuck Motorola, never again.
And from what I've seen in the Pro1 (no X), it works pretty well, does what it is supposed to. Price could be lower, but there is always something.
I got the Moto Z keyboard attachment, and it was too clunky to use compared to e.g. my current Pro1 or whatever I had back then (BlackBerry Priv probably).
I have no interest in buying a no-name brand phone, though.