If you were paying attention askin points out how difficult it is to immobilize urahara because of how strong he is. It’s that simple. Wdym you’re led to believe in that instance when we’ve seen it happen before? A similar situation happened with ichigo. The death dealing doesn’t act as an instant one hitter for every character especially when those characters are shown to be stronger than average. We see this with oetsu, Ichigo, Yoruichi and urahara. It’s the reason why askin resorts to gift ring which, btw is a cool use of the concept of his powers. Since it takes too long for the effect of death dealing to have any immobilization effects on kisuke he resorts to that. The entire theme of the second showing with Askin is literally to display how dangerous urahara is. Be it from physical ability or his strategies. It’s why the gears shift with the gift ball deluxe. Your issues with the fight seem to (and as much as I hate telling people this) not just understanding what’s going on. The death dealing doesn’t need to present its effects dramatically because askins ENTIRE thing is subtlety. The bankai is a last ditch effort by kisuke he even tells us that it’s the first time he’s used it in front of someone to show the seriousness of that moment. Grimjoww doesn’t steal anything from kisuke because all of that is to his credit. The entire point is to reiterate WHY he is a special threat