Let’s say you’re a toy manufacturer, making major bank on a line of Godzilla figures. You’re going to want to give your consumers all of big G’s most iconic nemeses, and then, for some mysterious reason, you’re going to make up a gorilla monster and release it in roughly the same scale. It’ll totally not be King Kong, even if the character is public domain and there’s nothing stopping you. For example, Medicom put out “Atomic Kong” in 2015. King Kong isn’t atomic, so they’re obviously different.
Then there was the time Marusan had the classic character “Giant Gorilla”, who’s just snapped out of his chains. He had a couple different incarnations. Granted, this was during the 60s, before the whole public domain thing.
Who can forget the time Y-MSF supplemented their impressive mid-2000s Godzilla line with Gorosaurus, the giant octopus, giant snake, and “Gorilla Monster”? Or Raymundo’s “KK” and “Mecha Gorilla” toys? “KK” could be a lot of things… maybe it was meant to be a figure of Kazuki Kitamura.
This Iwakura figure is of a “demon god”, so I don’t see how anyone could even think it resembled anything else.
And of course, to clash against Imperial’s Godzilla (the toy every American child had for decades), who else but the iconic “Hong Kong Gorilla”? Because of the giant gorillas they have in Hong Kong, obviously. Like in Mighty Peking Man. There’s no other reason for including “Kong” in his name.
And then Bandai, creators of the SH MonsterArts series-
…oh, you messed up, Bandai. Anyway, it’s usually easy to distinguish official King Kong merchandise from goofy knock-offs. The real King Kong toys are the ones that have glowing skulls and can shoot missiles from their chests.
Maser Patrol 
Dude, King Kong is NOT Public Domain!!!!!!!!
Kong’s tortured IP status as a character is covered in some detail over the course of the series of articles this is a part of. In short: it’s flip-flopped all over the place over the years, but the status of the original novelization presents a loophole that lots of people have been able to drive a truck through, and things get even muddier when you get into international markets. This, of course, won’t stop anyone from suing about it, though.