SVG - reuse a line node with <def> and <use> - svg

Question

My goal is to re-use a line node as follows:
<defs>
<desc>x1 and x2 values never change, would like to provide y1 and y2 in use</desc>
<line id="p" x1="5" x2="1019" stroke-width="1" stroke="#808080" opacity=".3"/>
</defs>
<use xlink:href="#p" y1="718.5" y2="718.5"/>
In learning SVG I thought any parameter provided in the use statement was passed to the template in the defs, but apparently not? According to W3 docs:
The ‘use’ element has optional attributes ‘x’, ‘y’, ‘width’ and ‘height’ which are used to map the graphical contents of the referenced element onto a rectangular region within the current coordinate system
However, 'use' is supposed to support "Any...graphical element...", line included. Well, line doesn't have x,y,width or height attributes; it has x1, y1, x2, y2.
Also this would preclude passing in all sorts of other attributes like stroke, stroke-width, etc.
Is the use statement really limited to just x,y,width, and height or is there another way to get attributes merged into the def template node?

Answer 1

Since line is neither an <svg> element nor a <symbol> element it is covered here:
In the generated content, the ‘use’ will be replaced by ‘g’, where all attributes from the ‘use’ element except for ‘x’, ‘y’, ‘width’, ‘height’ and ‘xlink:href’ are transferred to the generated ‘g’ element. An additional transformation translate(x,y) is appended to the end (i.e., right-side) of the ‘transform’ attribute on the generated ‘g’, where x and y represent the values of the ‘x’ and ‘y’ attributes on the ‘use’ element. The referenced object and its contents are deep-cloned into the generated tree.
So width and height are ignored and x and y become ways to translate the line. That's basically all you can do with it.