It might be perfect if the withdrawals can't be deposited or the person would not make a deposit again. And I want to say that the real winning can't be counted/measured until we stop gambling. If we do not stop gambling then at any time we may lose what we had and what we had earned. So, the withdrawals can't be considered as the real winnings.
If a person cannot make deposits ever again then how will he gamble further? I think the point here is that people are tempted to play with their profits or money stored in their casino accounts, so in order to not to over gamble, they should withdraw the money from the gambling site and deposit only what amount they require to gamble.
Well, this may be a good idea for a newbie who does not have control over his emotions, an experienced gambler should be firm in this plan and no matter how much bankroll he has at the site, he should never gamble only because he sees balance in his gambling wallet.
It's true, in several cases and from my experience, usually gamblers, including me, often feel tempted to gamble or to run a session when I see a balance in my gambling account, whatever the amount, it can still be tempting and break all the limits that I have previously made. This means that even though a gambler, for example, already has a plan regarding limits, that doesn't mean they will always really stick to that plan, because when they see the available balance in their betting account, various temptations will appear in their mind, where these temptations will give rise to hallucinations. looks tempting which indirectly, consciously or unconsciously, can make a gambler move and take action without realizing it.
Previously I was often trapped by this situation which in the end I lost all the balance in my betting account, and of course as you said, if it is the balance resulting from a previous win then it is clearly better to make a withdrawal first then leave a small portion for fulfill our gambling desires, because if not then it is very likely that they will use up the entire balance in the account until it runs out.