From my (not super reliable) knowledge, English is pretty popular ornamentally in Japan. English words are often thrown onto packaging or advertising and stuff like that, which catch the eyes, even if a lot of people can't understand them.
Would probably make sense on Masterpiece figures, as they are supposed to be a kind of royal collectable tier of Transformers toy. You'd probably see similar stuff on high end expensive Pokemon merchandise or other stuff.
Again, I have little authority, just going on what I've seen in Japan. I think we've been seeing a little of it in the west lately. Many brands and T-shirts and stuff like that have the Japanese word or whatever to attract buyers, even if they don't speak it, because it looks cool/exotic/authentic.