I don't like either FOSS or FLOSS. But I see where you're coming from. I think FOSS is not worth arguing over in terms of changing what people already within the community say (compsci is already filled with strange terms), but I also want to clearly communicate the ideas of the 4 freedoms to outsiders coming in which FOSS doesn't do to those already unaware. "Our community" is already really niche as it is and also has bad actors who want to erase the freedom aspect as much as possible and using unclear and confusing terminology is a real tactic (look at people calling LLMs and machine learning "AI")

Acronyms don't explain anything by themselves to people who don't already understand them. Your example works because it's already self describing, FOSS isn't as much.

No, don't toss it for FLOSS, FLOSS is the same thing and has the exact same problem as FOSS. Stop grouping them together entirely.

If you mean Free Software say Free Software, don't let that OSS sneak into the acronym