I just tried this scenario on the latest iOS PowerApps client and it worked fine. I could see true and false text displayed correctly. True and false are set as the TrueText and FalseText properties of the toggle control. Are you using the latest PowerApps client? Are you talking about the TrueText and FalseText properties of the toggle control?
Sorry i forgot to mention, these are in a form.
Form Width: 110.2
DataCard Width: 108
Toggle Width: 92
True Text: Safe
False Text: Unsafe
Chrome Web Browser:
iPad Pro 10.5 inch:
You can quite clearly see that the toggle has shrunk hugely.
Ive done more investigation on this and can confirm its not just a iOS rendering issue.
The Form displays fine in Studio (Web), even on preview mode.
On iOS it renders wrong, but also, by chance (as i never use) i also run the app in a browser from web.powerapps.com, and it also rendered incorrectly.