It certainly doesn't sound like something I would do to leather.
From your description, it doesn't sound like something that the shop should be doing to leather.
This can be a touchy situation when you don't agree with the boss, but in this case, I think I would ask him if you could try a procedure you had heard about on one of the jobs. He would probably be impressed/surprised at how the seats will look and if he thinks he can take credit for the "new" procedure, he shouldn't get upset with you. You might even do it on your own time so he can't complain about that. If it works like I think it will, he might even compensate you for your efforts. If he doesn't like the idea or doesn't accept the suggestion, you probably should just accept his rejection and start looking for an employer that will.