Just do it and don’t worry. You most likely will have no issues. Time alignment (if it was even considered in the design) on wee speakers will not be greatly affected and floor bounce off a stand mount is not factored in and doesn't give a boundary reinforcement thus is a non-issue.
odd question about stand-mount speakers
Is there any reason you shouldn't turn stand-mount speakers upside down and listen to them that way, as long as you use some kind of vibration control/decoupler between the speakers and the surface they're placed on? The reason I ask is because, at least in a near-field setup, I would think having the mid/woofer ABOVE the tweeter would enhance image height/size -- assuming the tweeter is kept at ear level. (A couple of asides: I don't currently have bookshelf speakers, otherwise I would experiment. Will likely be buying some in the near future though. Also, I know that there are some stand-mount speakers that place the mid/woofer above the tweeter, but the vast majority do not -- most of the ones I'm interested in do not.)