For all we know, the content still exists on the social media platforms' servers, and access is just blocked to the public, but the platforms will happily provide it to the proper authorities in response to an appropriate request.
(Of course, I can't rule out the possibility they may have physically deleted some of it, or may do so eventually – I don't know what their data retention policies are – but I imagine they would be hesitant to permanently delete content that may plausibly be of future interest to regulators – this article contains zero information on whether they have actually physically deleted any of it or not)
Human Rights Watch is of course a purely private body, so unless they reach some special arrangement with the platforms (and platforms are sometimes willing to enter into those sorts of special arrangements), they are not going to have any more access to removed content than the general public has. But that doesn't mean that government authorities don't have more access than the general public has.
For all we know, the content still exists on the social media platforms' servers, and access is just blocked to the public, but the platforms will happily provide it to the proper authorities in response to an appropriate request.
(Of course, I can't rule out the possibility they may have physically deleted some of it, or may do so eventually – I don't know what their data retention policies are – but I imagine they would be hesitant to permanently delete content that may plausibly be of future interest to regulators – this article contains zero information on whether they have actually physically deleted any of it or not)
Human Rights Watch is of course a purely private body, so unless they reach some special arrangement with the platforms (and platforms are sometimes willing to enter into those sorts of special arrangements), they are not going to have any more access to removed content than the general public has. But that doesn't mean that government authorities don't have more access than the general public has.