Theme nesting does not work on v.5.0.3

[Uhmopt]

Hi.
I am one of the material-UI lovers.
The new version of this has very many useful features and I am very excited about that.
However, I have discovered one of the strange problems.
I am going to use the nesting theme feature on my project but it does not work.

https://mui.com/customization/theming/#accessing-the-theme-in-a-component

Many times, I have tried but the result is the same.
I already have used that feature of version 4 and it was really useful as your guide said.
However, now is not.
I hope to know why it is not working and how can I fix that.
Please help me.
Thanks.