fair point, usually when you think of a rhyme, you think of perfect rhymes! two words are a perfect rhyme when the last stressed vowel and any following letters are pronounced the same (kit and bit, picky and tricky, amorous and glamorous).
Addison and Larson are not perfect rhymes because the last stressed vowel (a in both cases) is not followed by the same letters and/or same pronunciation, it's all over the place!
you could make them perfect rhymes by stressing the -son:
Addi-son instead of Add-ison, Lar-son instead of Lar-son
but that sounds clunky- (unless you're a French speaker ig)
fortunately, Addison and Larson are still rhymes, just not perfect ones!
two words are a syllabic rhyme when the last syllables of both words sound the same, even though they might not be stressed (pitter and patter, speaking and hearing).
Addison and Larson are syllabic rhymes!