I have the same problem. While the dictation software seems to be the best I've used, I am not a child and don't need an app to give me permission to use big boy words. I hope there is an answer soon.
I'm not sure if this is an option in your settings with the galaxy S10.
This really depends on if Bixby is using Samsungs voice input for voice to text processing.
On my S9 I open system settings, general management, language and input.
On the menu that opens I select select on screen keyboard.
The new on screen keyboard menu has an item titled Samsung voice input. I select that its menu has the option to turn on or off hide offensive words. It's on by default.