What internal_url is used for (=how to correctly workaround removed base_url configuration option from tts)?

In HA 2022.7 the deprecated base_url configuration option has been removed from tts (Remove `base_url` configuration option from `tts` by emontnemery · Pull Request #94905 · home-assistant/core · GitHub):
The TTS base_url option which was deprecated in Home Assistant Core 2022.5 has now been removed. Configure internal/external URL instead.

The problem is that my base_url was different from internal_url:
internal_url: https://192.168.1.185:8123 - HTTPS with a self-signed certificate, doesn’t work with Google Home
base_url: http://192.168.1.185:8120 - HTTP served by my simple web-server like:
app.router.add_static('/api/tts_proxy', path='/home/homeassistant/.homeassistant/tts')

As a possible workaround, I have changed my internal_url to http://192.168.1.185:8120. Now tts works correctly (Google Home successfully plays my text messages), but I’m wondering what else I could break. Obviously, I have provided an incorrect URL for HA itself.

Thank you!