Bing Chat is wrong. RHEL customers are legally allowed to share the code. What Red Had can do, and that has nothing to do with the GPL, is to end the contract with the customer who shared the code, thereby according to the GPL the customer also no longer has any right to access the code. The GPL only applies to software distribution, not contracts outside copyright law.
Edit: Red Hat is under no obligation to share non-copyleft code of which there is plenty in a Linux distribution but they do. Just look at Apple: Take plenty of FOSS code, give back only a fraction. It sucks but it's legal. That's also why Apple moved away from GPL software – can't even bothered to ship BASH with macOS.