You do not know this for a fact. Apple test their phone under controlled conditions. Probably by just placing it gently in Pale of water not under the Fossett poring on it. Use a little screen spray cleaner and be done with it.
I never stated it as a fact it’s simply an opinion, your stating yours as well which holds as much weight as what I said. But as I said I would be more concerned with corrosion in the charging port than the seals given the seals are there to protect against water ingression. There are no protective measures against corrosion against the contact points that I know of.