Phantom no kyc? UK tax thoughts.

Just set up a phantom Wallet on my sisters phone only to realise there is absolutely no checks done on the account owner. Let’s say someone on their own portfolio sends £3k to their sister Coinbase wallet let her withdraw it to her bank and send it to themselves. There’s no way HMRC will automatically know that the original £3k profit wasn’t really the sisters is there?

I know moonpay or whatever is connected thru kyc and that’s how ppl initially fund their wallet but are they really gonna care enough to dig that deep? Especially for someone who isn’t a whale and where this can be done thru creation of multiple fresh wallets to make source origin more difficult.

Also heard that Coinbase only reports transactions >£5k is that in single transactions or total?

DISCLAIMER: I DO NOT CONDONE TAX EVASION. I AM JUST CURIOUSSSS.