I don’t know when the next release will come out, but likely it will be “soon” (there may be a metric/American unit conversion in there somewhere!) which supports proper cloning.
Meanwhile, beware that the boot process has changed considerably from earlier releases of L4T and thus it is difficult to actually dual boot an Xavier (which is needed to do a true clone). @snarky probably has the best workaround until the next release:
An actual partition clone is usually better since a mounted system will have some pseudo files over the top of real files, but for the most part this isn’t an issue.
It used to be that extlinux.conf and U-Boot contained everything needed to pick a root partition, but some of that information is now needed in earlier boot stages and some of this has migrated to partitions and device tree (meaning a serial console picking an entry in extlinux.conf probably isn’t going to work as expected). It’ll be interesting to see how the boot process evolves at the next JetPack release.