I think Fe users
use feeling; its for practical purposes. Recognising and responding to emotions in others, judging the vibe of a situation, increasing their understanding of behaviour. Its a tool to navigate the world with. For Fi users, especially Fi doms, their feelings arent necessarily practical. Theyre compulsive, overwhelming, and colour their whole existence. Their lives are built around exploring and enjoying their rich inner emotional world.
Putting it differently, perhaps Fe users are more detached from feeling and prefer to use it constructively. Fi users dont care about that, they just want to
feel as much as they can.
[Edit] Its why Fe users can seem fake in their emotional expression to Fi doms. Ive experienced that a few times, suspicion from Fi types.
[Edit Edit] My ideas on this have come about from comparing INFJ and INFP... another explanation for the difference in functionality could be that for INFJs feeling is auxiliary and so is more of a supporting function, whereas for INFPs its dominant and is basically their whole way of being.
[Edit Edit Edit] Actually I think thats the real reason

For instance ENFPs or ESFPs would use Fi in an equally functional way, to sort out their perceptions and determine their value/utility. Use it as a tool, a guide. So my OP was basically wrong but hey, I'll get 'em next time.