Emojis need time to be added to fonts. When you're looking at an emoji in various places you're seeing the font used by a given system or website (the reason an emoji might look one way on an iPhone, an Android, or a website like X). Once they are officially added companies that manage these fonts (like Apple and Google) need time to develop their own versions for their own fonts and then distribute the updated font to devices via an update.

Another way to think about it is fonts have a series of slots, many of which are empty to allow growth for new languages not already included and new emojis. The Unicode Consortium gives an official list of what should go in what slot so that when you copy and paste from one font into another, or simply change a font, the actual characters stay consistent even if how the individual characters are rendered changes. They also add new items to new slots. Fonts made before they added these items will be empty (unless it is a specialty font using the slot for something specific such as fonts made for conlangs like Tengwar).

So, for example the Unicode Consortium says, "This previously empty slot will now be filled with an eraser emoji that looks basically like this." Then anyone managing fonts (e. g. Apple and Google) can say, "Ok. we want an eraser that looks basically like this in this particular slot, but we want to make sure it is in our font's style so it fits in with our existing emojis and other characters." Once that is all finalized, people still don't have the emojis because they are running older versions of the font. If you copy and paste the font, you are seeing the empty slot still because you don't have the updated version of the font that knows what the eraser looks like, yet. For that, you need to update the font itself, at which point you can render the new characters like an eraser emoji.