If I transfer some BTC from an exchange with KYC to an offline wallet without KYC are tax agencies just going to count that as cashing out and require capital gains tax?

Maybe it's a dumb question but if your BTC goes off the Tax Agencies map are they going to require capital gains tax as if you cashed out? and will you need to provide proof that you still just hold it in BTC (on your secure coldwallet etc) to avoid them making the assumption that you just sold it?

They have a record of you buying x btc, you made a withdrawal, and on their traceable record you now have 0, the difference between BTC when you brought it then withdrew it will now get legally stolen,

As far as I'm aware in my country you only need to pay capital gains when selling the crypto for fiat or other cryptos and not when it's still in the same coin so I still wouldn't be required to pay tax if it's still just BTC