WHO'S GOT THE SCOOP ON RESIDUAL VALVES?

If you dropped your car off at my shop with the stuff in the trunk, I'd pull a w/cyl apart checking for "correct " spring expander, check size, install.
If the w/cyls are expander style then a redundant valve in m/c is of no consequence.
If old style regular poor fitting spring in w/cyls, it would be prudent to install a residual valve in the m/c, or there are many residual valve avail to go in the brake line.
But there can be no guarantee about manufacturerers, many breeds, many styles.
I'd like to note the old "rubber"seals of decades ago., prob hardened up pretty quick compared to newer rubber/composite "cups" of today.
Many vehicles I work on prob don't have residual valves at all, cept maybe "roll-control".
Let's consider worst case, minor amount fluid seeps out over long length of time. There is a sealed cap to limit volume of air to release fluid.
You regularly monitor your fluid levels, at least annually, or should, fluid loss should be noted.

jmo