It's not a weird request. OP or someone that does want to do it is trying to avoid the hassle and drama that the casino will give to them if ever they want to withdraw later on. I think it's not about any amount that you're about to withdraw but the emotional effect to itself is giving that anxiety for the gambler that why they have to delay the withdrawals just for the KYC when you've asked for it earlier but they don't want to. What's weird is that they should allow this to happen knowing that once they trigger the withdrawal button and asks for it, they'd still ask for it and you have to obey on it for which you've already prepared for.
Its normal request for a user since there are people willing to comply more earlier since what they believe is they can avoid any further issues if KYC has been submitted already. But submitting our KYC early doesn't really mean we are safe from troubles since there still instances that this will be ask if casino find something issues happening in our accounts. But since OP is look at FJ which is reputable so far I guess he just follow the recommendation of the support then continue to gamble if he's comfortable enough for doing it even if his request has been denied.
That is true that early submission of KYC doesn't mean that we're not going to experience some troubles. There's still a possibility that a gambler will experience such and will be asked for more and additional documents whichever is going to take that situation based on the casino that you're playing. And with FJ as OPs choice, it's a good casino and it's known with reputation that has been long here in the forum.
I understand the point of OP on why he want to request that but I guess each casino follow their rules and everything will be asked in proper time. For withdrawals issues when KYC has been asked I guess that is one of the consequences needed to go on and we just make sure to submit everything needed when KYC has been asked so that we can lower the waiting time and make sure that there will be no further delays will happen.
They have to obey what rules they have and as a customer that wants to proceed to kyc too early if not yet asked, also needs to follow the rules just as them.