Always wondered about clear coats and car leather too.If the paint finish is 'chalky' and dull then a polish can help. I have only seen chalky finishes on red and white cars. Clear coats are common place since the 1990's, I'm no expert but I'm under the assumption that everything now is base coat with a clear.
If you rub an area with a cutting compound and your rag turns red, then there is no clear coat. If it does not turn red, or the colour of the car then there is a clear coat. But you don't want to rub too much and cut through too many layers of paint.
Makes me think the majority of car care products are snake oils as for leather you just need to keep that top coat going and for exterior it's likewise.
I plan to protect my 156 one way or another this year, I've never polished or waxed it in 7 years which is disgusting of me! Might give ceramic coating a try once I've removed all the various swirl marks and road muck. I can throw a sheet over it in the garage so it should stay looking good for a reasonable amount of time...