I also can't access the mysql directory.
$ podman run -dt -v ./mysql/data:/mysql:Z centos:7.9.2009 sleep 36000
[root@97605e49f7e3 /]# useradd mysql
[root@97605e49f7e3 /]# su - mysql
[mysql@97605e49f7e3 /]$ ll
total 44
-rw-r--r-- 1 root root 12114 Nov 13 2020 anaconda-post.log
lrwxrwxrwx 1 root root 7 Nov 13 2020 bin -> usr/bin
drwxr-xr-x 5 root root 360 Sep 23 01:50 dev
drwxr-xr-x 47 root root 460 Sep 23 01:51 etc
drwxr-xr-x 3 root root 60 Sep 23 01:51 home
lrwxrwxrwx 1 root root 7 Nov 13 2020 lib -> usr/lib
lrwxrwxrwx 1 root root 9 Nov 13 2020 lib64 -> usr/lib64
drwxr-xr-x 2 root root 4096 Apr 11 2018 media
drwxr-xr-x 2 root root 4096 Apr 11 2018 mnt
drwxrwxrwx 2 root root 4096 Sep 23 01:48 mysql
drwxr-xr-x 2 root root 4096 Apr 11 2018 opt
dr-xr-xr-x 1369 65534 65534 0 Sep 23 01:50 proc
dr-xr-x--- 2 root root 4096 Nov 13 2020 root
drwxr-xr-x 11 root root 60 Sep 23 01:50 run
lrwxrwxrwx 1 root root 8 Nov 13 2020 sbin -> usr/sbin
drwxr-xr-x 2 root root 4096 Apr 11 2018 srv
dr-xr-xr-x 13 65534 65534 0 Sep 22 10:01 sys
drwxrwxrwx 7 root root 4096 Nov 13 2020 tmp
drwxr-xr-x 13 root root 4096 Nov 13 2020 usr
drwxr-xr-x 18 root root 80 Sep 23 01:51 var
[mysql@97605e49f7e3 /]$ ls mysql/
ls: cannot open directory mysql/: Permission denied
[mysql@97605e49f7e3 /]$ ls tmp/
ks-script-DrRL8A yum.log
[mysql@97605e49f7e3 /]$