This seems to be a feature. We see the same issue when using Genesys Enhanced TTS

https://developer.genesys.cloud/forum/t/delay-between-voice-prompts/2753

is an old thread that Melissa responded to saying the "delay" is only about 0.1 seconds. However if I'm building up a sequence that has something like "between a and b" where each item in that phrase is separate TTS prompt, the spaces there seem to be more than a naturally sounding gap between words.

It comes through something like "between.... a.... and....b". It is a pretty short gap still but not ideal. Has anything happened since this prior thread that may let us tweak this behaviour at all?