I think there may primarily be a communication thing going on here. But that said, I kind of have to agree with old JohnyEnglish on this to a degree and I understand where he is coming from.
Yes, kickboxing is a generic term and can encompass many different styles and rule sets. And clearly MT is a form of kickboxing (among other things, they kick and they box!). But when I trained and fought in New Zealand, it was well understood that there was "kickboxing" and there was "Muay Thai". Kickboxing was understood to mean a style that did not train or use elbow in competition but it did still focus a lot on clinch work. Muay Thai used the elbow and were permitted to do so in tournament. There was an acknowledged divide and difference and there were many schools called "Kickboxing" and the rules for tournaments were pretty much identical.
What I am trying to say is that in some places/countries people in MA will instinctively know what "Kickboxing" is and what to expect when going to a club or entering a tournament (although always check the rules!) and they will see Muay Thai as different.
To be honest I would be surprised if that is not the case in most places and perhaps people are being a bit semantic...or maybe you (and others) are genuinely saying that if a mate where you live said "I'm off to the kickboxing club tonight", you would be confused or not sure if they meant Muay Thai or savate or something else?
Sure you could say, "hey is that a PKA kickboxing club or something else?" But if a guy is doing Muay Thai he's going to say, "hey, I'm off to Muay Thai tonight (because "kickboxers" are too scaredy-cat to use elbows)"