Proper technique to adding a wire to existing pigtail
It doesn't really matter how the wires were before.  The wire nut is gonna reshape the wires when you crank down on it!
The #1 blunder with wire nuts is being too much of a softie and being afraid to use the nut to reshape the wires.  You have to!  If you don't, the wires won't mesh firmly, you won't have good contact, and the connection will overheat, arc and start a fire.
A properly done nut should pass a &quot;pull test&quot; -- hold the nut and yank on each wire, one at a time.
If a nut fails a &quot;pull test&quot; then it's either a problem with technique, not tightening enough, not lining up the wires evenly, or using the wrong nut - i.e. using a wire nut right near the extremes on its bell curve.  Go up or down a size, please!
If somebody's going for &quot;tape&quot; to keep wirenuts from falling apart, they usually think they are doing a great job securing it, actually they have a bad connection to begin with that is likely to melt and burn up from arcing.  The job isn't to physically hold the wires together, it's to electrically do that.