If rule B extends rule A and rule A is changed by an incremental compilation the changes in A don't also affect B as expected.
Fixed by https://github.com/droolsjbpm/drools/commit/3d3042bf6
Also this 2nd commit is necessary to fix this issue https://github.com/droolsjbpm/drools/commit/38c9e9ab12125144c4409a417daa21eb097bd192
Verified in BRMS 6.2.0.ER3.