No, you don’t need another device: You get an unique URL for each Unique speech (including text, pitch, speed, pauses, etc). And those URLs are SHARED between TTS devices if there the exact same speech with the exact same settings.
So creating a device for each text would be pointless.
You create a device for each output-device you have, each speaker you want to speak alone oon, and/or create a device for which the trigger will send the url to all speakers.
Because for each TTS device you link it to a speaker/device through a trigger and a action card sending the url.
Ofc you could use it differently when using H.O.O.P. (Hope) - Homey Object Oriented Programming
