As someone who speaks Cantonese, it’s more that Cantonese has six tones, rather than similar-sounding vowels. People who don’t know how tonal languages work are prone to fucking it up, cuz we have relatively quite a lot amongst the more popular languages. Plus the large number of homophones cuz of the monosyllablism of Chinese languages where each syllable has its own character, you get a lot of context-dependent words. Also makes for some puns, but yeah.