Not necessarily; while I'm not the most credible source on this: There are lots of instances where the Japanese have use English and has simply become part of the medium. I've seen many Japanese games and such use stuff like "Ready?" or "Stage Select", or even a small sentence like "No damage". Lots of Japanese songs incorporate English snippets in their songs, look no further than anime or even vocaloid songs, it's not out of place to hear some English words thrown in. While I myself can't give a true answer, I can assume it's because America has had and still has such a profound impact on the entire world's culture, it's possible the Japanese just adopted some words into their media assuming it can be easily understood; don't get me wrong, it's still in 99% Japanese and unreadable, you'll still find English thrown in, not as a joke but for a reason I don't know myself, I assume it's for the sake of space? But one can argue that Japanese text takes up less space which is why some games are preferred for speed-running in Japanese because of the faster text crawl in comparison to English text which requires more space since it's spaced out much further and that we don't mesh words all too often, sure we have "Don't" for such but it's not like we're coming several complex words into one like Japanese does. I'm rambling. It's not out of place for these things to occur; since Cave Story's translation, the AGTP version is technically cosmetic, no maps are tampered with, you can play a Japanese/clean copy of Cave Story untranslated (if you know it to heart you can get through it pretty easily), get to the the Iron Head battle and you'll most definitely see "No Damage." It's just stuff the Japanese do.