Well, depends how the pocket door was installed. If they used 2x4 with studs turned it would give you 1-1/2" (+1/2" drywall) to attach screws to. If they use a kit with metal channels and small amount of wood to attach the drywall to, there may not be enough wood to apply a fastener that would support a table. The wood in those metal channels is pretty narrow so you have like 1/2" to 3/4" of wood there. It really is meant for drywall only.

You can measure the door jamb on each side of the pocket door to estimate how much framing you have to work with. Do not use screws that are longer than what you have to work with or it will damage the door and/or make the door not able to open and close.