As a follow on question about solder paste;

If the SMT parts are glued onto the bottom side of the board, and thus are held
into place with the glue and not the paste itself, How can a proper solder
joint exist?

SMT parts on top of the board are seated down to the surface of the board by
gravity/convection.

If glue holds SMT parts, won't these back-side parts be permanetly held off
the surface of the board? and thus require a different solder-paste approach?