Incorrect ZFS file system 'atime' property in zpool

Hello,

Despite having set the atime property to off for the root pool, several file systems are mounted with atime=on from initramfs (container names are redacted):

# zfs get -r atime
NAME               PROPERTY  VALUE  SOURCE
rpool              atime     off    local
rpool/ROOT         atime     off    inherited from rpool
rpool/ROOT/alpine  atime     on     temporary
rpool/home         atime     on     temporary
rpool/lxc          atime     on     temporary
rpool/lxc/<c1>     atime     off    inherited from rpool
rpool/lxc/<c2>     atime     off    inherited from rpool
rpool/srv          atime     on     temporary
rpool/var          atime     on     temporary
# 

This is not how ZFS should work, importing the root pool should honour this setting, as it does on Solaris and FreeBSD.

I guess this is not necessarily Alpine related, but a more generic Linux problem because of how Linux boots with initramfs, then does a pivot_root. Though Solaris (and derivatives) works similarly with its boot archive. Issue #8609 (closed) looks related: the resolution there seemed to cause this.

I tried a workaround by adding rootflags=atime=off to default_kernel_opts in /etc/update-extlinux.conf, then ran update-extlinux and reboot, but it did not help. Maybe I'm missing a point.

Edit, addition on 11.2.2021:

It seems like it affects non-root zpools, too. I've reinstalled the server meanwhile (for other reasons, out of scope) and here's what I can see currently (redact.sh just replaces the poolname):

 zfs list -t all -r | ./redact.sh                                                                  
NAME              USED  AVAIL     REFER  MOUNTPOINT                                                 
linux_sda4       4.59M   221G       96K  /linux_sda4                                                
linux_sda4/home   124K   221G      124K  /home                                                      
linux_sda4/srv     96K   221G       96K  /srv                                                       
linux_sda4/var   2.11M   221G     2.11M  /var                                                       
# zfs get -r mountpoint,atime,canmount,mounted | ./redact.sh                                        
NAME             PROPERTY    VALUE        SOURCE                                                    
linux_sda4       mountpoint  /linux_sda4  default                                                   
linux_sda4       atime       off          local                                                     
linux_sda4       canmount    noauto       local                                                     
linux_sda4       mounted     no           -                                                         
linux_sda4/home  mountpoint  /home        local                                                     
linux_sda4/home  atime       on           temporary                                                 
linux_sda4/home  canmount    on           default                                                   
linux_sda4/home  mounted     yes          -                                                         
linux_sda4/srv   mountpoint  /srv         local                                                     
linux_sda4/srv   atime       on           temporary                                                 
linux_sda4/srv   canmount    on           default                                                   
linux_sda4/srv   mounted     yes          -                                                         
linux_sda4/var   mountpoint  /var         local                                                     
linux_sda4/var   atime       on           temporary                                                 
linux_sda4/var   canmount    on           default                                                   
linux_sda4/var   mounted     yes          -                                                         
# mount | grep zfs | ./redact.sh                                                                    
linux_sda4/var on /var type zfs (rw,noatime,xattr,noacl)                                            
linux_sda4/srv on /srv type zfs (rw,noatime,xattr,noacl)                                            
linux_sda4/home on /home type zfs (rw,noatime,xattr,noacl)                                          
#                                  

So:

1. no matter if I set atime=off for the whole pool, the mountpoints do not inherit this
2. the output of zfs get and mount are contradicting each other: atime=on vs noatime.