Must say I don't really understand why some feel inclined to deny the existence of "guaguancó de salon" or whatever we should call these. It seems pretty clear they exist beyond just as covers and references to rumba guaguancó. I'd be much more interested in exploring the connections...
Thanks a lot Richie for asking Sonny Bravo! The guajeos do seem like the most distinct feature.
Regarding terms like "son-guaguancó", I seem to remember reading it somewhere referring to one of Arsenio Rodriguez' variants of son, and then connected it to recordings like Oiga Mi Guaguancó or Lo Que Dice Justi. It's quite possibly not an established term, although it doesn't seem completely wrong either to label those guaguancó de salon as they are-related.
The best reference I could find just now is from
http://www.lajiribilla.cu/una-propuesta-de-ruta-para-el-son-cubano/ -- I'd guess there's some better sources backing this.. .
That search also led me to Celia Cruz' 1966 album Son Con Guaguancó, which features two guaguancó de salon (Son Con Guaguancó and Tremendo Guaguancó), labeled just "Guaguanco" on the sleeve. Here's an earlier guaguancó de salon she recorded with La Sonora Matancera in 1961, Sabroso Guaguancó