The only Canon breech lock I've used did not meter in aperture priority and was always in stop down mode on the F-1 which made focusing accuracy debatable. I never liked working in stopped down mode, but sometimes that just how it goes.
Sounds like it was either a defective FD mount lens or an FL mount lens.
The chrome ring breech lock FD mount lenses provide open aperture metering on an F-1. With the right finder, they also permit auto exposure on the F-1. They were first made available with the F-1, which was followed by the TLb and the FTb and the TX and the EF, with the latter offering auto exposure.
The chrome ring breech lock FD lenses also provide open aperture metering and auto exposure with the AE-1, AE-1p and A1. The AE-1 offers shutter priority auto-exposure, the AE-1p adds a program mode and the A-1 further adds aperture priority automation - all with the chrome ring breech lock FD lenses.
When the AE-1 was introduced, Canon introduced a new version of the breech lock FD mount - the "new FD mount" - which behaved more like a bayonet mount lens, but technically remained a breech lock mount. The chrome ring disappeared and the process to mount a lens changed, but the mount itself was essentially unchanged - still offering open aperture metering, and the capability of providing shutter speed priority, aperture priority and program auto exposure.
Back in the day, I sold a whole bunch of FD mount cameras and lenses to a whole bunch of customers
. I've used a few of them as well.
All of the above applies to the typical FD mount lens. However, as another poster has mentioned, a tilt-shift FD lens probably can't offer open aperture metering, because with the tilt-shift mechanism involved, there would be no way of maintaining the required mechanical connection between the aperture setting mechanism in the lens and the open aperture metering lever on the camera and mount.
