Why does SVG upload in Media Library fail if the file does not have an XML tag at the beginning?

It seems that in the recent releases of WordPress, changes were made to the mime type handling to make sure that files have the extension they say they do: https://make.wordpress.org/core/2018/12/13/backwards-compatibility-breaks-in-5-0-1/

This poses an issue for SVG files without the tag in them.

SVG is actually an XML, and WordPress is now requiring to have a line such as 

<?xml version="1.0" encoding="utf-8"?>

 in an SVG file.

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