By using the mobile new controls (with crosshair and action buttons) and breaking a block in creative, the block will flicker and not break. By holding down attack on the block it will usually break, though sometimes it just doesn't. I have found that the block usually breaks if there is another behind it. I have gotten more than one person to test to verify it is not just my device, or my resource/texture packs. You can use the flicker of breaking to force yourself into crawl, (which is kind of useful at times), or clip through blocks. It would be nice if the blocks just broke how they were supposed to, though.