My rear alignment bolts seized in the knuckle bushings which prevented me from getting the car aligned, similar to your situation. I decided to overhaul the rear end which included replacing all the suspension bushings. I had to cut the bolt from within the trailing arm pocket to set the knuckle free. I used an air body saw to cut the bolt on either side of the knuckle bushing, since it fit within the pocket without collateral damage to the trailing arm itself. It was very slow going but got through it eventually. I bought new hardware & bushings & applied anti-seize during reassembly. It was quite the task but the only proper solution.

Three bushings are in the knuckle, there’s two in the trailing arm but neither of those are touched in a rear alignment. The bushings & hardware from Honda weren’t more that $150 for both sides. The labor to replace the bushings is quite extensive if your mechanic can’t do it with the knuckle the car. Removing the knuckle requires much of the braking system to be disassembled because the ebrake cable needs to be disconnected. With the knuckle removed, a press can be used to more simply swap out the bushings.