> speaks a significant amount of Japanese and they don't even know it
Only for a very loose definition of "speaking"
A Chinese without knowledge of Japanese reading it or vice versa would be like a English speaker reading French or vice versa. You'd recognize some vocabulary, but the grammar and pronounciation is significantly different and most of the overall sentence is still foreign.
Even English loanwords are significantly altered by shortening and mapping to Japanese tones. Most English speakers wouldn't recognize "terebi" (television) or "konbini" (convenience store) for example.
Not to mention some words like パターン (pataan/pattern) have either very specific meanings that an English speaker would not understand naturally or other words like テンション (tenshon/tension) have completely different meanings that an English speaker would not recognise as English.
Only for a very loose definition of "speaking"
A Chinese without knowledge of Japanese reading it or vice versa would be like a English speaker reading French or vice versa. You'd recognize some vocabulary, but the grammar and pronounciation is significantly different and most of the overall sentence is still foreign.
Even English loanwords are significantly altered by shortening and mapping to Japanese tones. Most English speakers wouldn't recognize "terebi" (television) or "konbini" (convenience store) for example.