The angle of elevation has to be used in conjunction with the rotation value.
It is clamped because it describes the angle of the sun from the world centre respect to the ground plane and will always be between -90 and 90. Straight up and straight down or less. The rotation value describes a circle around the world center.
The “sun position” add-on lets you go over mid-day using the time slider.
When you play with the time slider the addon adjusts both the elevation and the rotation value.
To get the sun to do the whole day going over 12 O’clock (90º) you have to adjust both values.
There is a mathematical relationship between them (rotation and elevation.)
My maths suck so I much prefer the addon for this, also I find it very logical.
First you set the North offset to decide where north is (best to do this at sunrise or sunset), then it is a simple question of changing the time of day. This is easily animated and physically logical.
I can not imagine a logical way to do this with an empty, it would be easy to set the sun to the position where you want it for one frame by rotating x and z but you would have to work out an equation (that uses the rotation of both the empty’s z and x axis) to set the values for an animated day, as you would have to rotate the empty on both axis at once it could be a nightmare.
It would probably be easier to first set an initial sun rotation value and elevation (like the addon’s north offset) then rotate the empty on a single axis using drivers to “add” the values needed to the sun nodes rotation and elevation values. (Which is what the addon does for you with the time slider)
Math makes my head hurt and I have no idea of the correct driver settings, you may even need to add a script with “if - else”. I would probably prefer to look into the addon’s code to see how they did it!
My advise would be to use the addon as it is great