Yes, that is true. But, like I said, that's BOTH rear brakes. If only one is locking, that problem is between the T block on the rear axle and the rear brakes. Even if the metering valve is messed up, it would effect both rear brakes equally. It sounds like you have more than one issue here.
The metering valve requires the brakes to be bled in order, so that the metering valve sets correctly. Passenger rear, drivers rear, passenger front, drivers front is the correct bleeding order.
But even if the metering valve were misadjusted, it would effect both brakes equally. In the rear at least you have one problem that's between the "T" and the rear brake. Air, brake line issue, brake line adjustment or contamination.
