I don't know what they do now with the CNC made parts and assembled components. Maybe it makes no difference anymore as a lot of things are assembled on or by machines now.
But,,
The rule of thumb for dovetails is they enter from right to left.
Drive them out of the dovetail from left to right.
That goes for sights, dovetail parts attachments, spring bases, ect.

If the dovetail is on the bottom of a part like a forend escutcheon dovetailed into the bbl, left and right reverse when you turn it over 180* to work on it.
Disregard that reversal of L&R when you flip things over to work on them.
Everything is fitted as you are looking at and working on that part.

Fitting is done to allow a bit of free start of the sight or part into the dovetail so it lines up nice and straight before the hard fit takes over.