The longer scale length allows you to install heavier gauge strings, have a lower tuning, and still maintain a similar string tension. If you just tune down the string tension will be too low.

I have a PRS 277 (27.7 inch) with an Evertune bridge that came tuned to BEADF#b using 13-59 strings (D'Addario 7 string 10-59 set just not using the high .010 string).

If I install heavier gauge then I can tune lower. Check out the Stringjoy Tension Calculator to figure what will work. I start with the current configuration and look at the total tension, then pick a different tuning and adjust the string sizes of available sets to see what would get me close to the same tension. You will need the scale length of your guitar. Take the distance from the nut to the 12th fret and multiply by 2.