verifyta behaves differently when invoked with
verifyta -y -t3 -o5 mdl.xml mdl.q
verifyta -y -o5 -t3 mdl.xml mdl.q
It is indeed specified in the docs that -t3 enables -o4 automatically, but this option can only be overriden when -o5 comes _after_ -t3.
It took me a while to figure thit out and thus the suggestion to document this or to treat the switches on the command line independent of the order of occurrence (switches grouped with their arguments, of course).
This is a documentation issue. The behaviour is as intended.
Added a comment about this to the verifyta -h help screen.