I've been looking across broad numbers of searches on accounts which have their content identified as "sensitive content" and have noticed that some tweets do not appear in the search as would be expected. While they do not appear in the search when using Twitter without an account, the same search does show all expected tweets when done using an account. The missing tweets seem to always contain media, whether video or image(s), but other media still shows up with the "The following media contains potentially sensitive content" warning.
My primary question is whether there is any discerning factor as to what will and won't show up media-wise on a search. Basically, why do some pieces of media get hidden behind a warning while others are completely omitted?