Look inside http://cdimages.ubuntu.com/daily-live/current/ the ISO for arm64 is dated 2021-03-15 08:22 while the one for amd64 is 2021-01-23 08:36
they are 2 bugs for this problem: https://bugs.launchpad.net/ubuntu-cdimage/+bug/1919079 and https://bugs.launchpad.net/ubuntu-cdimage/+bug/1918929