This is just completely the opposite to what i've experienced within Claude and Gemini. Sources are identified and if inaccessible are not included in the citations. I recently tried a quite specific search aimed towards finding information about specific memo's and essays cited within a 90s memo by bill gates, and it was succesful at finding a vast majority of them, something google search failed with.

I don't want to say that it's a skill issue, but you may just be using the wrong tools for the job.