That is not the issue. The issue is that users expect the emoji they send to look the same to the receiver.
Geeks know that emojis are "characters" and therefor might look slightly different in different fonts. But this is not how the average user sees it. They see emojis as small images and expect them to transfer unaltered just like any other image they put into a message.
Course I find it silly that they swapped a real gun emoji for a water gun. How will my friends know I intend to go hunting and not play water guns with my nephews or whatever.
When they were really simple icons, it made sense to treat them as characters. But today they are detailed illustrations.
On the other hand, that'd be dependent on connectivity.
[0] https://blog.leahhanson.us/post/recursecenter2016/haiku_icon...