Even if you did disclose it, it's not up to them to interpret how you practice your faith. They may try to make an argument from authority, such as: "Well the majority of Christian leaders support the vaccine, so there's no reason for you not to do the same" but where does it say that you have to conform to the mainstream belief of any particular faith? It doesn't.
Still, I'd highly recommend disclosing as little as possible at all times so that you don't somehow "incriminate" (crazy that it has to be put that way) yourself in a way that will be used against you if it comes down to it.

There are a few key things to do:

• Remain courteous and polite at all times. Never say more than you have to at any given time, no matter how close you consider your boss or co-workers. This is vital.
• Research, research, research. From researching letters and the law, all the way to all the information you can possibly gather about Covid and the vaccine that you feel helped you form your belief. This is more in preparation than anything. Don't get caught off-guard.
• Document everything. I do mean everything. You can even record conversations as well if single-party consent is applicable in your State.
• Ensure you have proof of delivering your exemption letter. Again, you can record or have them sign a copy. Get creative but make sure you can show that it was delivered. A witness would likely work as well.
• To give added "umph" to your letter, get it notarized. The reason I say this is because by getting the letter notarized, you are swearing that the content within is one-hundred percent truth.
• Before answering or agreeing to anything be sure to say you'd like some time to think. Use that time to find out what direction they're trying to go.
• Overall, just be smart. We can only do what we can do. Assume the worst and hope for the best.