If you are reading this review you already have a suspicion of what these specials are.
Yes they are NSFW,
Yes they contain full frontal nudity of the girls,
Yes you are unleashing your inner perv by watching these,
No there is no story relevant to the main series,
No you won't regret watching these (or your inner perv won't at least)
No there is no reason to feel ashamed watching these
There is fanservice in almost every (mainstream) anime and VN these days. You can watch Grisaia censored or uncensored and in doing so not forcing anybody unconvenient fanservice upon them without their knowing (come on if you see
'uncensored version' you know what to expect to some degree =p)
But for anyone still wondering I shall point out, these are uncensored, so be prepared, and enjoy!