It's an impressive achievement but I'm not sure I'd call that a whole brain. It's a larval proto-brain with less than 4% the neurons of an adult fly.
What's completely crazy in this research is the ability to thin-section fly brains. Thousands and thousands of slices _of a fly brain_, good old physical science at the heart, crowd-sourced to connect the dots (though I'm not positive that's the case in this paper). The open-hardware imaging tools used in some studies like this are also super cool- https://openspim.org/.
For instance, if you expose larvae a rewarding stimulus like sugar along with an odour, they will later be attracted to that odour. That is by definition learning, simple learning, but we have to start somewhere i guess.
Interestingly there is some evidence that the memory lasts through to the adult stage, despite the fact that a lot of the brain is actually rewired during pupation.