If you go to the ElevenLabs homepage to test their voice chat, you can select a language. Genuinely love to see multilingual options.
Then you look at the dropdown.

English. American flag. No British English option. No anything-else English option. Just English, and English means American. That's the whole tell.
Once you clock it, it's everywhere.

The voice transcription I'm using right now to ramble about, well, whatever I was rambling about, keeps inserting Oxford commas. I don't write with Oxford commas. Most British English writers don't. But the system has decided that the formal, structured way to render speech is the American way, so that's what it gives me. It's also transcribing "tonne" as "ton", because of course it is.
Two platforms, same assumption. Multiple times a day, every day. The defaults are quietly encoding whose English counts as English.
I'm going to keep a list.