I am an INFp, but I can be quite unspontaneous too though. My other INFp friend and me like to play safe many times (like we love staying at home and are kinda scared of new experiences etc.) and I remember meeting an SLE guy at a party and I couldn't open up at all at least that fast within a few hours time (too much pressure for an introvert), and even though I am very humourous with my friends and people I trust.. it takes me time to show Fe towards someone that intensely, especially if I am attracted to them and do not want to come across as weird.
Even other INFps I met are not Fe in your face, I guess it takes a while for introverts to show their Fe at all.. it's often used very subtly. And even though I can be soft and flexible with people I do not wanna piss off or whom I really respect, I am not that diplomatic at all, actually Si and Ne users are much better at being diplomatic and not insisting on things, I as an Ni/Se user am very stubborn and want to reach my goals no matter what, sometimes just waltzing over other people's feelings (I am not Fe dominant afterall but a dominant Ni user). I sometimes do not understand the stereotypes about INFps.. yes, we are soft and stuff.. at the same time we are not as good natured as the internet portrays us and I learned a lot of the social rules from other people as I often just disregarded them to get what I want.. especially as a kid.