The Phoenix travels on the Phoenix platform. When the Phoenix travels away, only the word "Taiwan" is left. The next line of the poem is that the Phoenix has left the platform and the Kongjiang River flows by itself. Together they are "Taijiang"
Another reference:
The mystery uses the offset method: Phoenix Tour on the Phoenix Platform. The phoenix cancels out the phoenix, leaving "on the stage".
The answer uses an offset pattern: the answer contains related words related to offset such as: drop, go, not, province, nothing, move, etc., so the answer should be interpreted as: Taiwan/Taiwan Province. Omit the word "bay".