There is a clear advantage of using a liquid membrane it is relatively easy to apply over the tile substrate along with the use of a fiber mesh tape you can secure joints and changes of plane.
Wall tile vapor barrier.
X 1 5 mm premium silent underlayment for vinyl plank laminate hardwood and tile model 22491 125 00.
A vapor or moisture barrier is a layer of protection that is designed to act as a waterproof shield helping to keep condensation away from wood insulation and other mold prone materials that are located behind the drywall.
Water vapor that gets behind walls or travels up through light fixtures or hvac grilles into an attic will turn back into water when it cools off.
A vapor barrier can be applied or installed over the tile substrate using a liquid or sheet membrane.
Steam stays in a gas form until it cools down or hits a barrier such as a shower door tile ceiling or a mirror.