I don't think that there is an action that would load audio or ui late.
So they should be safe against the reporte issue.
On the other hand block-* has the way of hotplugging the first disk of some kind that will load the .so file then. So I'd assume this is how you have hit this issue?
The current list of extra .so files that we have are:
## Package: .so files ##
qemu-system-gui: audio-pa.so, ui-gtk.so
qemu-block-extra: block-curl.so, block-iscsi.so, block-rbd.so
I don't think that there is an action that would load audio or ui late.
So they should be safe against the reporte issue.
On the other hand block-* has the way of hotplugging the first disk of some kind that will load the .so file then. So I'd assume this is how you have hit this issue?