One thing about Sanchez Vicario is she was a bad matchup for Graf, and with Seles out and the WTA elite in many ways crumbling starting 1993, she ended up playing Graf an awful lot more than she would have. So alot of people seeing her great matches with Graf, combined with her 4 slam titles she ended up with after the Seles stabbing, developed a false impression she was a better player than she really was. For instance she had a much better head to head vs Graf than an aging Navratilova, post stabbing Seles, and Martina Hingis, all who are much weaker players than Graf (one could speculate on peak Navratilova or peak Seles, but that is aside the point). To have 3 years where in a weak field the only one better than her was Graf, someone who she was naturally a bad matchup for her to boot, was the ideal dream situation for her really. I think her other head to heads with top players probably give a stronger indication to her true abilities, which is not up to a typical 4 slam winner.
Kind of similar to how Capriati's head to head with top players are shocking for a 3 slam winner, and indicate she probably overachieved to reach that, but people mostly remember her great rivalry with Serena who she was a bad matchup for her, and thus was made to look better than she really was against, and even delude some people to thinking she was better than a typical 3 slam winner. However atleast Capriati's success is pretty much unquestioned by any outside event (Seles was never going to be still winning slams in the 2000s, stabbing or not).