Why are files with wrong character encoding name write-protected?

I'm unable to delete the files with [wrong character encoding in names](https://android.stackexchange.com/q/249146/94084) on my phone. I plug it into my Windows PC and try to delete it in File Explorer. It says the files are write-protected:  [This guide](https://www.youtube.com/watch?v=I79JQewqs00) tells me to

su
restorecon -v -R /data/media

The output is

u0_a82@j1x3g:/ $ su
root@j1x3g:/ # restorecon -v -R /data/media
Function: selinux_compare_spd_ram , priority  , priority version is VE=SEPF_SM-J120H_5.1.1_0069
SELinux: Loaded file_contexts from /file_contexts
SELinux: Skipping restorecon_recursive(/data/media)
root@j1x3g:/ #

But the deletion still doesn't work. Nevertheless I can do this via adb. Do you know why this happens?