I just wondered from a technical point of view what causes it.
So if the standard glyphs (the icons) they use for whatever reason don't load (there can be loads of reasons for this!), then your browser is basically like, oh crap, theres nothing there! Better fill it, so it falls back in this case to using apple emojis. So it's not left just blank
Basically the non-technical way to describe it would be, you come to my house, you ask for a fork, I panic, I have no forks! So I throw some chopsticks at you. It'll do!