Is it true that some authors spend time describing a character eating breakfast or the texture of toast?

[Joeing]

It's prolly for the visual. Doing it sparingly will help the readers ground in the world. So they have some general idea of toasting is like in that world. (could be otherworldly toast if the setting isn't based on real world).
Not sure if that contributes the plot, likely unrelated.

 

[Clo]

Stimulating all senses is good for immersion. Sound, texture, taste, smell, colours...

Some people have fond memories associated with taste, and writing about it can help you reach those emotions.