Terms like that can definitely have a wide range of implications on how people visualize it, particularly with physiques. You're right of course in how you defined some of these things for yourself that many would agree with.
The issue then becomes in my earlier gripes on tagging how we can properly define these people for everyone's perception by placing them in their "best fit" category or combination of categories like you would for say music. It's like how someone is tagged as "fbb" but not "muscular woman", both don't necessarily overlap as they have different meanings but they can as a muscular woman may not necessarily be a body builder but a bodybuilder is often seen as being quite muscular due to their defined muscle physiques. Meanwhile a powerlifter will likely be larger due to strength with larger parts of their body, but as they may not be visually defined muscles they may not be tagged as "muscular" in my experience and instead simply receive "strong woman" as another tag example if nothing else(I'm pointing out my experience in how tags have been used, whether "correctly" for some or not for others). This can go on and on of course with plenty of debate if only because certain words and definitions can vary/overlap even when they're written out to how people visualize/describe them.
Getting base tags is probably the most annoying bit though, especially in how people think on how they should be used like female bodybuilder(fbb) when they aren't "officially" one(not that you need to be I think, pro cards seem annoying to get after all but are a huge achievement). Just some mildly relevant random examples. I'd probably say for example that
Lora Cross is fit but also slightly muscular because she has notable biceps when she flexes them and occasionally slightly visible abs(she fits your definition well, but can also potentially get tagged with muscular). While
Brickhouse00 Tina Rodriguez(wish to find more big women like her who do XXX) is definitely muscular but is also an ffb because she gets in contest shape and competes. Meanwhile
Simone Steele(love her, huge inspiration) is very muscular but is not an fbb because she doesn't compete I think(probably could if she tried) but would still likely receive the tag due to her general physique but in contrast wouldn't necessarily have the fit tag.
I don't know, maybe I'm just over thinking(realizing 3pgs later.....). At this point it seems more like with terms like "fit" and "muscular" there might be a threshold in which someone has them both applied or just one when they meet/exceed perceived criteria/expectations. Same with fbb regarding what people perceive/visualize as being a bodybuilder's physique. I don't think for example the word "fit" comes to people's minds when they see
Amazonka(beautifully huge physique, videos are a little terrifying to me with her expressions) for example lol. Still annoying to label, but without no one finds anyone(especially in this niche for fit/muscular women).