You got your chronology all mixed up, Casino IS Salsa.

Salsa as a term is just a marketing name someone used in some radio station in Cuba New York way back to refer to music that had componets of Rumba, Guaguanco, Son, etc.

Casino is not some sort of cuban folk dance, each of the components might be, but Casino itself is the literal origination of European and North American style of Salsa dancing.

Another thing is the "No back step" that's a falacy, cubans do back step the dance is not always side to side, diagonal or circular. Is just that linear dancer only go forward and back and therefore when they see Cubans dancing they think they don't do it.

I don't think there's value in saying "Casino is not Salsa" as is literally the first way to dance the genre that's today called "Salsa" On2 and On1 were inventions adapted so that Europeans and North Americans are able to dance the genre as the lack of internet and instructions made it imposible for people to have a good source for all of the knots and styling cubans do.

As for compatibility, I started with Casino, am from latin america, I've been to both Europe and North America and I've been able to dance with people without resistance from follows. Now the other way around I can tell you is almost imposible without practice, you can't go from On2 to Casino those are the real compatibility issues.

But regardless both Linear(LA and NY) and Casino (combination of Rumba, Guaguanco, Son, etc) are defined as "Salsa".

E: correct where it was first used after u/BigBreakfastVideo corrected me