There are many homonyms in Chinese languages, though the poem above cheats a little because many aren't genuinely homonyms due to the different tones, also, many of the characters used aren't modern characters that are used in every day speech.

'Shi' isn't in Mandarin only. There is significant overlap with other Chinese languages, so there are going to be many words with the same sounds, some of the words in the poem above will sounds identical in Cantonese for instance.

'Shi' is also used extensively in Japanese (sometimes even overlapping with Chinese). In addition to being used 'numerically', it can be used to emphasize a point, to connect two words, and can be used for several completely different words e.g. death, poem, city.