From personal experience with a male that had to patrol boundaries constantly... and we had Joe 47 years. Yes, abrasion occurs, however a terracotta plant saucer is very unlikely to cause serious damage just surface scratching.
If something like a water bowl is obstructing a stomping route then relocate it. Put the dish in the middle of the enclosure rather than the edge or in a corner. Boundaries are for patrolling, so don't put things on a boundary that you don't want marched through over.