Action button of type MultipleCheckboxes disregards the condition rule that defines when it should be visible. It is always visible. When the action is changed to mode ActiveRecord, the rule works.
Tested on versions 2024.5.2.3449 and 2025.4.0.3771.
This is the expected behaviour as compared to the ActiveRecord mode. For ActiveRecord the RowStates are resolved for the active row. With MultipleCheckboxes the active row state is not important, because the active row doesn’t necessarily match the selected row. In this case any validation has to be added to the action defined for the UI button.