Not at all. I treat link-shared notebooks as “unlisted” and only publish them once they are polished enough. However, I frequently import from these notebooks, both in link-shared and published notebooks. I also occasionally share these links through various public channels.
My concern is really only with the attribution, not access to / forking of unlisted notebooks. Please note however, that new users in particular often fork and immediately publish notebooks because they are simply unaware that they can import from link-shared notebooks (see also this topic).