The Specification for aria-current=Step
"A step token used to indicate a link within a step indicator for a step-based process, where the link is visually styled to represent the current step."

Both aria-current page and step are described in the normative text of the specification as associate with links. It is more lightly that aria-current page will be applied to a link, however this is not necessarily the case, for example, the current page in a breadcrumb is usually not linked. Arguably aria-current location should be used for a breadcrumb, but, you will find that 'page' is used more than 'location' on breadcrumbs.

The problem I see is that aria-current step may not be linked, and this would be an acceptable pattern, for example, a progress bar showing the current step in a purchase journey, in my experience, is not usually linked.

I recommend that the Spec for 1.2 be changed to "A step token used to indicate a step within a progress indicator for a step-based process, where the element is visually styled to represent the current step."

Would like to see a discussion on extending this to other values on inactive elements.

Reference
Accessible Rich Internet Applications (WAI-ARIA) 1.2 > aria-current (state)