I wouldn't worry about staining as much as I would about fireclay's inability to take a punch or a repair. Drop a cast iron skillet one time and you could be toast. At least use a wire rack.

Kohler still sells a boatload of cast iron apron front sinks that don't stain with racks available.

I had the white apron farm sink. Never had stains but boy did it scratch. Luckily they came out with elbow grease

I have one (Rohl) installed four years ago and I love it! I do use a rack and I’m careful with it. I chose not to have a disposal because I read they can cause crazing.

No they don't stain easily however it can cost $5000 if they break to replace, A apron front sink like a cast iron Kohler is a safer choice. Read this blog:

https://www.mainlinekitchendesign.com/general/fireclay-farmhouse-sinks-and-pot-filler-faucets-recipes-for-disaster/

Kohler Whitehaven Apron Front sink