Can a line of two points be a closed path?

Question

Design

How is it possible that a path through two points can be closed?

Answer 1

I'm not familiar with Illustrator, but apparently the Close Path button draws the B-A line. And if you pull up the mustache, you will see that there are two lines.
I repeated the same thing in Inkscape: I drew a segment, switched to editing curves (Edit path by nodes), selected both ends, clicked "Join selected endnodes with a new segment" - the line became double. If you drag it behind the line (the segment does not have a mustache in Inkscape), this will be visible.
In the same way, you can draw a "biangle" with the "pencil" and "pen" tools.
Yes, and "closed" here is not "closed", but "closed".
PS Looked closer; it can be seen that the anti-aliasing of the curve means that there are exactly two lines on top of each other.

Answer 2

Why not?