Doesn't curry specifically refer to a sauce with yoghurt?
Nope! Although that's probably one of the most popular example styles in the west, it's not an exclusive distinction. Plenty of light, more savory curries out there (but I'd hazard a guess that most do at least use ghee, because ghee is magic and one of the four basic food groups along with curd, rice, and salt).
Salsa is just sauce, but Curry is either from Old English for Cuisine, or Tamil (Kari) for charcoal. Neither of those tells anyone anything, so you have to go with the understood meaning as opposed to defined meaning.
The split comes when the defined meaning in Europe/America is different and more specific than the defined meaning in India (or Thailand for that matter, but I don't know anything about that). In India, curry just means sauce. No, it doesn't tell anyone anything. Neither does "masala", which means "mix (of ingredients/spices)". You're still going to be offered masala dosa or thali with multiple curries. Which curries? What masala? Pffft, fuck you, eat it and find out!
We'd regularly eat lunch at a place that served rice with curry, masala, dal, fry, pickle, and sweet. "Dal" is the most descriptive of any of those, since it infers that the food article will contain lentils of some form. Details beyond that are guesswork. Fry means anything that's been fried. Pickle is... Pickle is pickle. I don't really know how to describe it offhand. Sweet is, you guessed it, some kind of dessert.
Everything changed wildly on a daily basis, but they still fit within the bounds of those categories... Because those categories are nebulous as fuck and aren't really even expected to tell you anything about what you're gonna eat.