I've been to Japanese restaurants in Korea and Taiwan, and they still say irasshaimase despite no one working there being Japanese.
Why didn't you make a thread, bro.
The article makes it seem like he's trying to replicate authentic sushi chef banter, which would very likely include a Japanese sushi chef saying "delicious!" to some foreign customers because it's a common English word every Japanese person knows, rather than 'mocking' an accent. The word 'delicious' is within the Japanese lexicon, and it's written and pronounced 'derishyasu' when incorporated into the language.
I live in Japan and my native language is English. There are dozens of times a day where I have to use English words which have been incorporated into Japanese, but if I say these words in a typical English way then they won't be understood. If I tell the taxi driver to take me to "Bandai bus terminal," the reaction would be a puzzled look because it's "Bandai basu taminaru" in Japanese. Those words are English in origin, but they have been incorporated into Japanese and effectively become a new word. I'm not putting a Japanese accent on English words, I'm just speaking Japanese words.
If you find me a random guy who doesn't know any better that's just swapping l's with r's with zero context, then I'm with the outrage. This guy just seems to be speaking Japanese.
Edit: I get that what he did may be offensive to some, but the current trend of hit piece articles that are obviously written just to get someone fired is becoming gross. "This guy WHO WORKS AT THE EXXON STATION AT THE CORNER OF APPLING AND HIGHLAND was very rude when I saw him yesterday at the Gap."