Can I fail the test if I remove the parking brake on an auto?

Yes that's an instant fail, replace the cables they commonly seize

Did you first slacken off the handbrake inside to let the cables go back to their position of rest , adjust the shoes and then check the handbrake .

We would see if the cables move easier when slackened off or its hitting the hub and cant move anymore as someone justs adjusts the inside.

If both sides are equally terrible it will probably still pass

If you're totally happy the cables & linkages are ok, I think you'd better strip the drums again. Look to see if there's a black stripe run mark on the shoes in which case they aren't making full face contact. Chance sanding the marks only to allow more of the shoe to touch but ideally replace the discs.

It's only a telescopic bit that extends the outer cover of the front cable to remove free play. The thing with worn cables though is while the may seem free under no load, they'll bite in to the outer cover under load & reduce the pulling power.

Only other thought is that you need to release tension completely on the front cable BEFORE you adjust the shoes. Adjust shoes until the brakes lock up & usually release about 6 clicks

It also literally said parking brake performance which is not necessarily about imbalance but equally a fail.

That's more down to the tester than the test, I'd say. Some of them might give the lever an extra tug to make it hold.

Personally I'd like my car to remain where I left it.