It seems pretty harmless, but if everyone did it, there would be less chairs, umbrella's or space in the spa for those who paid a lot of money to stay at a Disney resort and enjoy these items. Not that that was intended here, but it's similar to people who place towels on pool chairs to use much later; or groups that cut in line to meet up with others (in their group) and they're not considerate of those who stood in line a long time only to get pushed back a little further so the cutters aren't inconvenienced by being split-up.
The "black and white" rules weren't put in because they don't serve a purpose; they were developed because a particular problem continued to grow and enough complaints were made that management took action. I (like most everyone) have taken "liberties" from time to time, but I try to consider if my actions could negatively impact others before I continue. I've probably unknowingly inconvenienced people that I didn't intend to, but if it's brought to my attention, or if I learn afterwards that I bent (or broke) a rule, then I just adjust my actions going forward...
It certainly wasn't TwisterMomma's intent to negatively effect other guests with this request and it took a lot of courage to ask the question given how sensitive the topic is. I hope she's able to find other activities her family & friends can enjoy during their vacation that's just as fun and relaxing...