I do it as a habit after being paid to do so in the course of restoring and repairing older US and European cartridge firearms for many years.
You could almost make a living by just repairing the damaged screws on otherwise nice pieces.
Nearly all of the mid grade and higher had qualified slots.
Our Parker, LC Smith, Fox etc shotguns had them on even on the lowest of grades.
So too the European made shotguns and rifles.
Most US (repeating) rifle makers usually didn't see fit to time the screw slots for some reason.
I think buyers of 'quality' have come to expect it (timed screw slots). Wether it is historically correct or not, they like to see it.
(Least their buddy point out the poor craftsmanship when showing his prize piece around at the next club meeting.)
You guys know more than I'll ever have time to think about learning about original L/R makers,,but my guess is that they thought little of screw slots lining up on most builds.
The occasional 'extra finish' piece would call for such touches,,but the average gun built on speculation to sell to a local in the course of making a meager living,,I don't think so.