Launched in August the Sonder Signal ST is essentially a steel version of their existing Signal Ti model - that's Ti = titanium of course.
You can check out Andi's Signal Ti review here.
In that review Andi's large test bike had a reach of 457mm. That was over a year ago now of course and things have lengthened ever so slightly to the current reach of 465mm on size large. On the size medium I have been riding that reach is 440mm. So it's not just the frame material that has changed over the last year or so.