Having neighbours water your flowers shouldn't affect how you use the red sprinkler; that sprinkler is only interested in how long since you watered your own flowers.
However, people have been reporting that their use of the red sprinkler has been affected by neighbours watering their flowers, and this is something the devs are aware of and are working on, because it wasn't meant to be like that.
well actually it was meant to be that way, they just realized it was a stupid way to do and decided to change it. which shows that they do pay attentiomn after the fact on some things, so kudos to them