It's fairly typical for the BBC to hold fire until the trial concludes and the legal restrictions around reporting are lifted.

I'm not sure I see the AP as having more "in depth" reporting, it just has a greater quantity of rolling reporting. Stories like "court case pauses for Covid alarm", "court case resumes", "Assange told to stop interrupting witnesses", "lawyer says Assange could be in prison for a long time" are not, let's be honest, adding to the total sum of understanding around the topic.