Hi igor - yes like Danny mentions, when a hole intersects a seam edge, the seam edge is actually part of the boundary and must be selected too.

One quick way to untrim everything on a surface with a bunch of edges is to select one edge, and then use Ctrl+A which will then select all the other edges, then hit delete.

In the future I'd like to make the untrimmer a little smarter so that it could figure out how to remove only a portion of a full boundary, but for now it only handles full boundaries including the seam edge if that is part of the boundary.

- Michael