During migration, libvirt is waiting for qemu to migrate. Moreover, it's waiting for spice to migrate too. The resume of domain on the destination was done after both qemu & spice are migrated.
The resume of domain on the destination was postponed until spice migrate too. Even though there is no real need for this. This resulted in long pause until domain was resumed on destination.
The wait for spice migration was moved at the end of migration process. Hence, the resume is done as soon as qemu migrates itself.
There's no big pause on the destination until qemu resumes.