Holding our coins in non-custodian wallets is still the same thing as staking if we maintain the discipline of not touching it the only difference is that apart form the increase in the value there is no extra reward in terms of quantity in the amount of holdings.
Holding bitcoin in a self-custodial wallet is different from staking bitcoin on a centralized exchange. Before you can stake bitcoin on a centralized exchange, you need to move your bitcoin to the centralized exchange where you want to stake it, which will give the centralized exchange access to your bitcoin, and your bitcoin will be at risk because you don't have access to the private key. The centralized exchange team can cook up a cock and bull story that their exchange was hacked and they lost all their assets to the hackers just for them to steal your bitcoin without you suspecting them. Holding bitcoin in a self-custodial wallet gives you full control over your bitcoin, and nobody can tell you any false story about your bitcoin because you are in charge of the private key.