Slider and Input for same Value – Should both be tab-selectable?

I'm working on a form where users are able to select a numeric value both with a range slider as well as a numeric input. (See mockup below)

Both inputs have to stay in the form which is a design decision that I don't have any influence over.

A mockup of a form containing both a numeric input and a slider for the same value

Currently both the slider and the numeric input are tab-selectable, which in my opinion, is redundant because keyboard only users won't get anything from being able to use the slider as well.

My question is whether or not it makes sense from an accessibility standpoint to leave the behavior as is or rather to change it.

Another important question is if I decide to give the slider a tabindex of -1, should I also add aria-hidden="true" to it?

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