I just noticed this a few days ago when checking a friend's dog feed. If you open in private window it still seems to allow. (browse normal to instagram, right-click, open in new private window tab)
Opening in a normal new tab should work as well. I think it's because clicking a photo normally uses client-side navigation (navigates with JS), while opening in a new tab will fetch the entire new page.
actually normal tab wasnt.. i was a little surprised