According to N8N :

Somewhat related but not as dangerous, I have found in my old house
several instances where two switches share a wall box. It seems that
it must have been common practice to take the "hot" wire, strip about
3/4" or so of insulation, and wrap it around the terminal on one
switch, then terminate the end of the wire at the other switch. Not
sure why this was done, perhaps large size wire nuts were not available
at the time?

To clarify: someone grabbed the insulation with the cutters at
one point, slide the insulation down 3/4", and then stripped the
end too. Giving two bare points on the wire. Right?

It's done because it reduces the number of connections, and makes
the wiring in the box more compact. If you have a good stripper,
it's easier than cutting pigtails, and some electricians use
it routinely.

This technique is still in use, and is mentioned in Knight at least.
It's called out explicitly as an alternate approach to more
classic pigtails using short pieces of wire.

I use it quite frequently - it hugely simplifies multi-gang switch
boxes, and is sufficiently useful to even use it for mundane things like
pigtailing neutrals in mid-string receptacle boxes.

For example, a five-gang switch box with only two wirenuts -
for common ground and neutral, and _none_ on the hot. Even
with the ground wrapped around one box screw in each box of the
gang, and the two big-multi-wire wirenuts for neutral and ground,
the box will seem practically empty.

There's nothing unsafe about it. In fact, by reducing wirenuts
and wire-to-wire connections, it's safer than a separate pigtail.

I'm compliant with all codes on pigtails, and then some. But
I don't actually _use_ short pieces of wire as pigtails.

It's described in the electrical wiring FAQ, where I called this
the "mid-strip" technique.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.