I think need against when gambling platform change suddenly with their term of service actually make difficult for user withdrawing their fund with huge amount.
I'm not sure I'm getting this right but are you suggesting that casinos can change their terms of service (rules) any time they want?! If this is what you meant then let me tell you this is not true. Any reliable service will notify its customers about the slightest change they may introduce to the ToS. Besides, any change should not have any retroactive effect. Any service which doesn't follow those basic rules is to be avoided.
I think what you assumed is not actually what he meant, what i think he meant is that, "we should or need to be against gambling platforms that suddenly change their terms of service, as such act can make withdrawal difficult, most especially for those withdrawing huge amount of money".
So going by the above which i believe is a clearer and easier to understand version of his comment, i would say that he is right, and you are right too as you both are basically saying the same thing, a reputable platform, (not just talking about gambling platforms right now, but by "platforms" i mean, casinos, exchanges and so on), will not just wake up one morning and put out an update on their terms of service and fail to inform their users of such a change, because any platform that does that can be sued by any customer who feels affected and decides to take up the case legally, so, it is very mandatory for companies to always inform their users of any change in the terms of service, no matter how insignificant it seem or seems.