In my opinion , a  Folding Smartphone (whatever the design is) that can unfold into a   15.6 inches  Tablet can be a true , or a real   [ Laptop/Tablet/Smartphone (ALL-in-ONE) ] machine, because with that  15.6 inches form factor ,   besides being a Smartphone , it can also serve as a  Tablet and it can also serve as a  Laptop . 

Currently , as of today August 2023 , there is no Folding Smartphone that can unfold into a  15.6 inches Tablet .  This and this and this and this  and this  and this  and this  and this  and this are a few examples of   Folding Smartphones that cannot unfold into a   15.6 inches Tablet. Hopefully , in the not too distant future , folding smartphones like  this or this or this or this  or  this  or  this  or  this or  this or this , can unfold into a  15.6 inches  Tablet .