Yes and no on the language argument. Written Chinese, sure, but Taiwan's Fuzhou/Hokchew-based dialects are far from the Cantonese of HK and neighboring Guangdong/_Canton_. These dialects branched apart very early, about 2000 years ago, and saying they are more similar vs mandarin is kind of like saying that French and Spanish are much closer than French and Italian because Basque is closer to French than standard Italian. Most commonalities in pronunciation are due to both dialects preserving some older Chinese pronunciations, but overall pronunciation and vernacular word choice are very, very different.