It is kinda different from when I have had a crush on guys, who would kinda flirt with me, but they are more like "playing with me" rather than having actual romantic feelings for me.
Unlike those "flirty guys", the "sweet guys" are not flirting with me.
I think they are just being nice.
Well... sometimes people might mistake kindness as being romantic gestures. (like "Is this person attracted to me, or are they just being nice?")
One case of that happening was when I had a crush on a guy, who was a friend of my brother.
I remember that one time, when he was being like "Oh, there is only one candy left in the bowl, but I think Goose can have it" and I felt like I started having a bigger crush on him because of it.
I felt as if every time that he was being nice, I fell more in love with him. (Edited to add: Because of that, I was sometimes thinking "Oh, please stop being so nice towards me.")
But well... he didn't like me back. And I guess he kinda sees me as a sister. (Kinda like the original The Little Mermaid fairytale, where the mermaid is in love with the prince, but the prince is like "You're like a sister to me")
And the fact that I'm his friend's sister, I guess he feels like he has to be nice towards me. He is also nice to some of my female relatives.
I don't have any romantic feelings for him anymore.
I still think that he is sweet and kind.
I have felt like these kinds of guys might be genuinely sweet and kind.
And maybe they would be considered "green flags".
But I know that there are cases of people being nice to me, but they are being mean to someone else.