Leading in a barrel usually only takes place when you use a high velocity load / followed by a lead load or vs verse...

Back in the day - 50 or more years ago, people made their own bullets and fired them out of their high power rifles such as a 30-06.
The home made bullets did not harm the barrel as long as you didn't try to use gilded bullets. The gilded bullets had more velocity and would heat up the lead deposits in the barrel and would cause pressure buildup issues.

As long as you only used lead or copper jacketed bullets and not both - it did not matter which you used and would not harm the barrel.

A sabot slug has a plastic jacket and is only against the slug as a shim to take up the space in the barrel. Just think of it as shooting a 20 gauge slug out of a `12 gauge barrel. The plastic will leave a small deposit of plastic in the barrel but nothing to be worried about.

Every time you shoot a shotgun shell - there is a plastic wad that travels behind the shot that pushes the shot down the barrel.
Its only job is to take up a space between the powder and the shot and to seal the explosion so the powder can propel the shot down the barrel. If there was no wad - it would just be like firing off a M 1000 inside of your shotgun barrel.

You don't have to spend a half a hour cleaning out a shotgun barrel so you can go between shooting sabots and slugs.
A squirt of foaming bore cleaner would probably clean it for you good enough if you was really worried about it.

How long does it take to squirt some foaming bore cleaner down a shot gun barrel and swab it out with a piece of old cotton tee shirt?