If you had included a capital letter, it would have been the full height. It’s really disorienting to have the text constantly changing height as you type based on the content. If you just typed a decimal point, should that be 1” high? In the height field you’re setting the height of the entire font, not just what you type.
The next release uses the equation entry control for font values, and doesn’t have the decimal appearing at the end problem any more.