StarCat

That phrase is just words, to understand whether it's manipulative or not you need to look at the context, especially at your usual relationship with the person saying it.

My mother uses a similar phrase, "Well, but I guess you just need to learn that for yourself." Sometimes she is really trying to lay a guilt trip on me... other times she's recognizing that she's trying to impose her opinions on me, isn't quite ready to admit that, and so that's her phrase to back out of the conversation as gracefully as she knows how.

To determine which one she's doing I need to pay attention to the tone of her voice and then the course of the conversation after she says that.
If she sounds manipulative, or if she keeps bringing the conversation up again throughout the course of the day ("One more thing I thought about..." etc) I know she's guilt-tripping/manipulating.
If she drops the conversation at that point, and her voice when she's saying that phrase and her intonations in the sentence sounds more like the interest and intonation someone would use to say, "But enough about that, let's talk about something more interesting!" then she's truly letting go and accepting that we don't see eye to eye on this issue.