If you want TTL (no BL) just set your flash to that mode. That is the normal method. When the TTL-BL mode is showing on the flash LCD just hit the mode button and TTL is the next mode selection. I believe spot metering takes you out of TTL-BL because BL requires the meter to read a large area of the scene in order to balance the foreground with the background. Spot metering will not allow that.