I have a feeling the DMC5 issue is one of an unintentional bug rather than censorship. In other words, the lens flare in the Trish scene was the original artistic intent, but for whatever reason was disabled in the unpatched version of the game across all platforms. Under this theory, with the most recent patch, the North American PS4 version has the "correct" lens flare enabled, while it is somewhat unclear the reason why the Japanese PS4 version and the XB1/PC versions still don't have the lens flare (unpatched? different patch version? still bugged?).
There are two strong pieces of evidence that lead me to this theory:
1) There is a second scene in DMC5 involving Lady which features the same type of lens flare obscuring her bare ass (the shovel scene). In ALL versions of the game across ALL platforms, this lens flare is present for Lady. Logically speaking, if Trish's scene is considered "censored", then Lady's scene is also "censored". But it doesn't really make sense for Lady's scene to remain censored if you're going to actively uncensor Trish's scene, right? In other words, if the artistic intent was for Trish's ass to be seen without lens flare, don't you think it incongruous that the same artistic vision decided to go the opposite way and cover up Lady's ass? Wouldn't Lady be uncovered as well? Therefore, given that Lady is covered in all versions, isn't it far more likely that BOTH Trish and Lady were originally intended to be obscured with lens flare?
2) The ESRB rating for DMC5 reads as follows:
>>>Content Descriptors: Blood, Partial Nudity, Strong Language, Violence
>>>Some female characters are depicted partially nude, with their breasts and buttocks minimally covered by blood, light, or clothing
The ESRB rating description specifically mentions that the nudity in the game is PARTIAL nudity (not full nudity), and that one of the obscuring methods for achieving this partial nudity is "light" (i.e. lens flare). Thus it seems quite apparent that the lens flare in both Trish and Lady's scenes were originally intended to be there, seeing as how those scenes got called out in the actual ESRB rating description. And as a corollary, it seems highly unlikely that full nudity with no covering was originally intended to be in the game, since the ESRB rating would have reflected that fact.