using man_made=breakwater does seem appropriate, however, place=islet should probably be removed then too shouldn't it? because if it is a breakwater, it is not an island or islet

It does not apply to all of those changes, but possibly some. However, I disagree with reverting the changes. It does not fix anything. If those are not really islands, that is a completely separate issue which needs to be fixed. I have no idea how to confirm that this specific one for example is truly an island or not.

I unfortunately do no know what Island this is supposed to be. I am making the assumption that the person who added it knew what they were doing.

I don't know. But I am assuming that the person who added it know that there was an island there. I just added the coastline tag because it is an island which is surrounded by ocean.

I would like to revert this change because I think I did it wrong. But I don't know how.