I noticed this while breaking Netherack with a stone pickaxe. You have to be really carefull to not destroy anything, as blocks break almost instantly, like in creative.

And this triggers some sort of a real bug, as afterwards it has a chance to apply to another block, too. Today, I got to the Nether, broke some Netherack, got back to the overworld and accidently touched an obsidian block of my portal with the stone pickaxe in hand and it immediately broke. It didn't drop anything but broke in milliseconds. Same thing happend some weeks ago to a block of cobblestone in the nether after breaking some netherrack.