cause sailing ships aren’t designed to take the full weight of the boat on just a few places were it is touching the ground. And in the long term (like probably years or so of doing this twice daily)the stresses this causes in the hull could indeed create weak spots and leaking.

Not to mention how it effects the liquids in all equipment which as well aren’t designed for this on a regular basis. Although with sailing ships they try to be more aware of it.

This is why if you see one of the Tall Ships in a dry dock (but also Yachts that go for the winter on the shore) to have blocks under the keel and stabilizers to prevent it from falling over. And even they are placed with care through a dry dock plan so the blocks are standing on places where the hull is already strengthened from within (and not every time on exact the same places preferably).

But to answer the original question, yes in the long run it can harm a boat. But for a relative short term(like a month), and on a tidal area where there might not be a place that is deep enough to keep floating during low tide this might be a safer solution than being half submerged every time. which is stability wise a very dangerous place to be.