A good yard, which is rare, will have prepped the areas where the keel
rests on the shoring while the boat is first hanging in the straps. Then they'll pick a time for launching when she can have a few hours of drying time in the slings before launching so you can paint these areas properly. The deluxe way, and expensive, is to have her lifted two or more times in the slings to work on these areas.
If the keel is metal, or otherwise robust, the keel shoring can be quite small in area. Exactly how small should be figured by an engineer
. Wood is good for maybe 500 psi so that 15,000 pound boat needs to bear on pieces of wood totaling only about 6" by 5".
And of course the yard will have used polyethylene covered carpet or cardboard or something against your hull
and not just some crappy piece of lumber
and bottom paint
encrusted straps. I never knew my old yard was such a bunch of slackers until I had it done the right way, elsewhere, for the same price