I assure you that conditions in the embassy are far gentler than the industrial slave processing centers that he would be housed in after a formal arrest.

You're unlikely to be raped by embassy staff, or shanked if you resist, for example. This is not to mention the myriad petty sadistic savageries that are endemic to the industrial processing of slaves in chains.

Shaking off the chains is far less easy than the morning dew, particularly if you're widely recognized as is Assange.