Is glass breakage on the back of iPhone SE (3rd gen) covered with AppleCare+

You can pay your deductible and get the iPhone replaced.

iPhone Repair - Official Apple Support

It will cost you $99 USD.

What you are getting confused by is that on the iPhone 12 and iPhone 13 they can actually repair the back glass for a similar price to the front glass repair on other models. This is not available on the iPhone SE, iPhone 11, etc.