BAT is for those on lifelong hormone therapy (and I'm not sure it has much credibility anyway). You're not on hormone therapy.
I don't understand why they don't want you to have your Testosterone back. If you don't know this, you need to ask them why. You've finished a curative treatment as far as I know.
Do they think it hasn't worked?
Do they think you have a high risk of recurrence?
Are you prepared to take the risk of cancer coming back sooner if you do have recurrence?