Fulltext query changed semantic

I've a test in the C# testsuite that fails with 12.1.4 and works in 11.0.9.

Seems that the root cause is a change in the semantic of the following query fragment:
"t.longDescription: ( +'beer' -'food)"

in 12.x means "(t.longDescription : (+'beer') or t.longDescription : (-'food'))"
in 11.x means "t.longDescription : (+'beer') and t.longDescription : (-'food')"