I'll note that MTG has an entirely different perspective on decklists. 'Rusing' is actually incredibly frowned upon, and you'll likely find decklists for major teams leading up to the Pro Tour. There's a couple of notable outliers, famed for deckbuilding skill, who keep their lists close to the chest, but in general the scene is way more open than Netrunner.
This is one area where MTG and Netrunner don't compare well, because secret decklists gives you way more of an advantage in Netrunner, owing to the bluffing aspect of the game.
As to this hack in particular... Mixed feelings. I don't feel it was cheating, but I also don't think it should be the standard. Then again, I never felt Scouting was cheating, either. The main takeaway from this, for me, is that there exists a Publish function for public decklists, and this Share Decklists feature was (probably?) intended for private, one-to-one, or within-a-group sharing. Published decklists are a display, while Share Decklists was a wall of featureless, unlocked PO Boxes that may or may not have a deck behind it, and it may or may not be a useful/viable deck. It's not, strictly speaking, illegal to look in an unlocked box laid out somewhere publically, but it definitely should feel weird.