The upgrades.minor field defines the upgrade behavior of the broker, see https://access.redhat.com/documentation/en-us/red_hat_amq_broker/7.10/html/deploying_amq_broker_on_openshift/assembly_br-upgrading-operator-based-broker-deployments_broker-ocp#proc-br-upgrading-broker-image-by-specifying-product-version-operator_broker-ocp
If upgrades.minor is true the operator should check the current broker container image and allow upgrades only between minor versions i.e. 7.9.4 to 7.10.1 is allowed and 7.9.4 to 7.9.5 is not allowed.
If upgrades.minor is false the operator should check the current broker container image and allow upgrades only between micro versions i.e. 7.9.4 to 7.9.5 is allowed and 7.9.4 to 7.10.1 is not allowed.

Actually, the operator doesn't check the current broker container image, the upgrades.minor field only affects upgrades where the version is equal to the LastMinorVersion defined in the operator source code:
https://github.com/rh-messaging/activemq-artemis-operator/blob/amq-broker-7.10.1.OPR.2.CR1/controllers/activemqartemis_reconciler.go#L2015
https://github.com/rh-messaging/activemq-artemis-operator/blob/amq-broker-7.10.1.OPR.2.CR1/version/version.go#L18