Yes, they are, but maybe not as much as Fes. They tend to accommodate on an individual level vs. being chameleon on a social level.
Fi is often described as a selfish or self centered function that only cares about itself and it's own feelings, and puts others last while Fe cares more about people, social harmony, and getting along. Most people don't take time to get to know how each of these modes actually operates. Instead, each judges the other using it's own reasoning or thinking.
I've been in so many situations where I suggest an idea, but because it's not in line with the Fe-lings of the group, it's dismissed. Or if you're not happy go lucky and "getting along" with group, and behaving as everyone else, your ideas are dismissed. This is Fe working against Fi. But then later, the dismissed idea is found to be one of the more productive ones. Fi is often less focused on whether it is liked by everyone.
I mention this as a way to explain Fi. Fi will share its views, but if ignored, will remain reserved or quiet. If Fi values someone's opinion, it will submit or set aside it's own feelings to accommodate them, especially if they care about someone deeply. I'll end up shelving my views to fit how they think. If I realize my views or feelings are not accepted, or is being ignored or dismissed, I'll simply pull back if I'm not close to it. But if I have to interact, I'll mirror the other person, rephrase, or repeat what they feel. That's one version of being a chameleon.
They'll rarely notice or they'll think I'm "smart" because I agree or support how they feel. That would be Fi version of being a chameleon, to keep our own feelings private, and just go with what the other person thinks. It's easier to do this one on one. Or I'll reflect the type characteristics that are more dominant. If T is dominant, I'll go T. If F is dominant I'll try to balance T and F more. That's another way it operates as a chameleon. If it's dominant F, then I'll show mostly F. So, depends on the environment and how people in that situation think or respond.
But these are learned responses based on the past. Since I received negative responses to expressing high Fi in social situations, I learned to pull back, and express Fe more. Fi has a certain emotional honesty or authenticity not everyone understands or appreciates, so this part is often hidden and shown only to those who are open, close to us, and receptive without judgment.
I notice that people with high Fe have a hard time accepting or incorporating Fi. Fe has a tendency to want Fi to just conform, while ignoring how Fi contributes in its own way. high Fe often has too rigid a belief about how things should be, and based everything on an understanding of how Fe thinks, and ignores how a difference in Fi's thinking can balance things out, rather than seeing it as entirely self interested.
Fi is not always assertive. It's a bit quieter and may become more visible only when describing feelings or when it's upset or expressing emotional needs (this is often the most problematic for Fe who views this as being childish or self involved). When I become overly expressive of my views, or I feel I'm overwhelming someone, I'll pull back.
FIs are often dismissed because they are not presenting ideas in a Fe-oriented manner, not popular or widely shared by the other members who may feel that any difference from the popular view creates disharmony. It's one of the reasons it's not always easy to share views or opinions. Fi's dislike confrontation, and after enough rejection or dismissal, they withdraw or walk away. If I have to keep fighting to be heard, at some point, I'll just resign myself, and not make the effort anymore.
However, I think INFJs maybe more obviously chameleon in their behavior because of Fe, while a Fi-dominant will likely remain quiet or more reserved if they are unable to express their feelings or views comfortably. Again, Fi's hate confrontation, so after a while, they'll clam up, or disengage completely.