Backed Enum narrowing error when using template

[ctrl-f5]

I have a method that returns an array that has a string key and a string backed enum value. When I define this shape as a template I get a type narrowing error, but when I type it directly I dont.

https://phpstan.org/r/f2fd19b9-2fc7-4b47-b5b4-11a8e3dce62a

I dont understand why the template route gives me an error, AFAIK I'm abiding by the template by returning a narrower type, or in this instance a value of the enum...