Generally casinos expect you to bet 1x or 2x before you make a withdrawal, so I agree that it is a bit excessive if they require you to bet 5x before making a withdrawal. Of course we are not referring to a specific casino, but usually this falls within the rules agreed upon beforehand when you create an account. One of the reasons I think is; The casino expects each of its new customers to play longer than the average for other casinos.
And it could be acceptable if the 5x wager requirements for collecting bonus. The requirement is 5x wagers only to enable withdrawal which is not for the bonus. I think it is too much and we have nothing to do except avoid the so-called gambling sites which have too many wager requirements.
I don't get you, did you mean that there could be a betting condition where you will use your own money and still be tied to a difficult condition of 5x before you can withdraw? If that is the case, then it's so absurd but I've not seen a thing like that in my gambling experience. It is in bonus offerings that some nonsense conditions similar to that are applied, which is more reason why I do not like to accept any bonus anymore in some of my accounts. In my sports betting account, I agree with a $0 bonus, but for casino bettings where I know I play mostly for fun, I still accept it to elongate the time of play.
The very reason why as a player, it is your responsibility to check the wagering requirements of the casino before you deposit to them. So if you think it is not fair like their withdrawal conditions, then, don't play on the site. Just plain and simple. They are not obliging you to play on their site, so it is your prerogative if you play on them or not.