The drone being bigger or smaller than the B-21 just appears to be a dick measuring contest at this point or should I say wing measuring. What is important is that it's a bomber sized drone, the outrage online about it being bigger or smaller than the B-21 seems like childish semantics.
Like what siegecrossbow said the exact size in relation to the B-21 doesn't matter. What is important is that it's bomber sized, and the relative capabilities it may have due to these size requirements.
Comparing it with B-21 is only useful in the sense that B-21 is the closest approximate sized aircraft of a similar planform so it's useful to say in shorthand that it is an "unmanned B-21 class flying wing".
I hope that people who have been so focused on comparing the two aircraft's wingspan only did so due to poor information on B-21s wingspan and quibbling over measurement methods, rather than hoping that GJ-X had a "larger" wingspan than B-21 as if that is worth anything, considering in every important aspect a few meters difference doesn't really matter.