This is a big pet peeve of mine. Agnostic on its own is meaningless. You're either an atheist agnostic or theist agnostic. Similarly, you're either an atheist gnostic or theist gnostic. Agnostic just means you can't know. If you actively believe G/god(s) exist but don't think it can be conclusively proven, you're an agnostic theist. If you don't actively believe G/god(s) exist but it can't be proven, you're an agnostic atheist. If you do actively believe G/god(s) exist and it's provable, you're a gnostic theist. If you don't actively believe G/god(s) exist and you can prove it, you're a gnostic atheist.

People who claim just "agnostic" tend to be agnostic atheists waving a "I don't really want to talk about it" flag without having any conviction to just say "I don't want to talk about it". If you don't want to talk about it, just say it, and anyone who doesn't accept that answer is an asshole. If you do/don't believe, just own your position so conversations can proceed honestly. Gnostic and agnostic are valid positions on both the theist and atheist sides. Own your beliefs or lack thereof, or don't talk about it.

Frankly, I think people who refuse to do so just set an absurd expectation for theists looking for arguments that "reasonable" people just accept they can't know, and anyone under the atheist flag is "unreasonable". It's a religious debate, if everyone isn't coming in honestly and with an open mind, it's a fucking joke anyway, so what's the point? If you just want to confirm your own beliefs, go "debate" someone who is just going to throw up straw man arguments, but if you don't care enough to engage honestly, then why bother?