Behavior of bulk edit product permission "to none" is not consistent with "from none"

When bulk edit product permission to viewer or product owner for example, product line permission of "none user" will change to the new value accordingly while other users will keep their their individually assigned permissions. This is a desirable behavior. 

However, the reverse is not true. When  bulk edit product line permission to none, all user permission will reset to none including users with individually assigned permission. In other words, bulk edit change is irreversible.

I can understand Aha! is trying to provide a way to reset all user permission to none but unfortunately  it sacrifices consistency. The same can easily be achieved by  providing a "Reset to none" option click box