If a SOAP 1.1 request comes in, it should be recognized (now it fails with an expception) and the results should be in a SOAP 1.1 envelope instead of 1.1
The two version are interchangeable, but the CITE tests use the one we do not support.
Actually the situation is a bit more confusing, the WFS 2.0 specification used SOAP 1.1 but the 2.0.2 corriggendum switched to 1.2.
I've also opened a ticket against the CITE tests: https://github.com/opengeospatial/ets-wfs20/issues/70
It's probably ideal to support both, as client might have been confused by these specs switches.
It actually seems to be more complicated, the WFS 2.0.2 specification uses elements of SOAP 1.1 in a SOAP 1.2 namespace for error reports, ticket here: