The "Current Job" Isn't Always What You Expect

% is the current stopped or background job, but not always the last one. If you've stopped any jobs, the current job is the most recently stopped job. Otherwise, it's the most recent background job. For example, try stopping your editor (like vi), then putting another job in the background:

% vi afile
CTRL-z
Stopped
% sleep 1000 &
[2] 12345
% fg

and notice that the fg brings your editor to the foreground.

— JP