/warning This comes off as a bit rantish so skip if you get offended, I just have the habbit of trying to fully explain my points/
If we are going to start slaying catgirls (Bringing real physics into this) then do keep in mind that Time is affected by gravity and velocity. While not specifically addressed many tests do indicate that both of these do affect time. This is scientific fact. Also as a science fact is that velocity is relative, thus the tests were affected by the earth itself, thus its gravity. by this thought the only way to remove time from an object is to either give it enough velocity (Basically have it moving faster then light, which is technically impossible by our current science, current studies of faster then light sub-atomic particles not withstanding) or remove all motion in the universe except on the desired targets, which is frankly less likely, and it would need to be universal as anything applying gravity would apply motion and gravity is not well known enough to say for sure that it has a limited range or what that range is. As current understanding of the effects of said force, we know roughly what it can do, and somewhat of what it can affect but most understanding is limited to things go down. everything else we know of it is more or less affected by observation or something else.
It is because of that that I define Time Stop as removing the effect of primary time from targets rather then stopping the entire universe. Frankly if Pluto could stop time in an entire Universe she would more or less be able to use her powers in other more dangerous ways. Like stopping a Youma in time so it litterally flys off the planet.
This is why I can see the unhinged ability being more accurate as it doesn't give Pluto insane powers and make her more dangerous then Saturn. Destroy that planet, sure I will stop the star its orbiting so it flys off into space and freezes.
/rant/
That said, this like all other things in Sailor Moon often use the attached phrase, "Because plot said so."
So nobody would complain if say *Ranma* (Replace with Random Non-Senshi) cannot survive in a Time Stop because they do not have Senshi powers. And nobody would really care if they could survive. It really is as plot dictated. Not to mention the fact that it was never touched in detail by anyone other then to say that it kills her to use it, and even then it has an amazing Deus Ex to get around, she reincarnates and time travels so its like nothing has happened.