The only chokes I've seen marked "lead only" are full choke lead choke tubes.
I would take what aftermarket choke makers say with a grain of salt- they are in the business of selling chokes- at $20-50 a pop, they are going to say whatever they need to get you to try their wares over the factory made stuff by the gun manufacturers.
About three weeks ago I cut about 6 inches off an old double barrel gun that the owner shot steel shot through and split the ends of one of the barrels. Now he doesn't have any choke at all on that gun.
Yes, older, as in much older shotguns don't handle steel well. If a shotgun was made in the last 30 years, I would shoot all the steel in the world through it and not have a worry.