Can a conventional seat be reversed 180 degrees to be used as a noseless seat?
If it works for you then go ahead.
The risk might come in a lack of control when riding hard, like descending while off the saddle it is common to use the sides of the saddle against the inside of one's thighs to help control the bike.
Separately you might need to angle the nose up sufficiently to get a comfortable position on the now-leading edge
Lastly, its probably not an issue for you but a reversed saddle on a rental bike means this one is damaged and needs some kind of service so don't rent it.