No subject

to stop for more than 120 seconds, which caused a kernel warning, but
the taint flags did not reflect that, it seems the existing taint was
simply reported in that message.

The taint flags in your log are P and O, which is "proprietary module
loaded" and "out of tree module loaded"
In the case where the snapshot would have caused the taint, I would have
expected to see one of those:
U Taint requested by an application
D Kernel OOPS or BUG triggered taint
W Kernel warning triggered taint
L Soft lockup occurred
None of those flags is present in your taint information, so it seems
your kernel is just tainted as usual, but not due to something having
gone wrong with the snapshot.

br,
Robert