PVC pipe will not hurt the monitors, but its also, of only some use. Indeed, it can provide a hiding area and it may, if used correctly, be used as a protection from dehydration.
On the otherhand, it does not allow for good temp regulation, too thin and even thickness and its of no use for exercising the monitor. Monitors are build to use their parts, like we are, they need to use their claws and attached foot, etc. Wood allows to strengthening of the foot muscles and provides some wear on the claws.
Hopefully you get the idea, while pvc pipe is ok, there are better ways to approach this problem. For instance, deep substrate, also provides shelter, to exact measurements and moisture control, as well as a constant source of exercise.
So natural materials such as hollow logs, dirt, limbs, etc are not only recognized by the monitors, but of multiple use and its better looking. Good luck FR