If the usage of the domains was agreed upon and they were to sell flowers, if for whatever reason I kept getting calls from random people checking on orders, I would be annoyed. It isn't a procedure that should be followed, rather a tip. This is due to the fact that there may be an internet savvy customer of the leasee who couldn't wait for a reply to a ticket/email and decided to call to check up on his or her order instead.
From personal experience, for the most part, we can all say that we've contacted a person using this route. Who's to say it can't be true?
I'm sure that anyone who leased a domain would be annoyed in the given scenario. In your instance, I'm sure it never happened, otherwise you wouldn't have mentioned it not being necessary. However, privacy with a couple registrars is free with a flick of the switch. With others, peace of mind costs $10 a year and could be factored into the price to cover it over the year (it's such a nominal fee, does it even matter to be factored?).