Earlier quoted context omitted.
Evidently, they have to formally question Assange before filing charges. They'd rather have him in custody in Sweden before they do that. Isn't it pretty well established by Assange's own actions that Assange would be a massive flight risk? The Swedish aren't the ones acting irrationally.
First of all, you can be charged in absentia in Sweden. If they interviewed him, and he still refused to return, then that would be a textbook case of a justification for having him charged in absentia. Secondly, he claims that he will be extradited to the US if he is brought to Sweden. How exactly would he suddenly become more likely to try to flee if they decide to charge him? He is already claiming that going to S…
OK, maybe it's a little irrational that the Swedish prosecutor doesn't want to bend over backwards and do it Assange's way just to humor his paranoid delusions. But it's not suspicious.