According to :

Just curious. How do you which are which? I have never seen anything
printed on the packages. I have always twisted wires. That's how I
was taught many years ago. It's easier not to twist, but twisting
seems to make the best connection. As for wirenuts, I dont see how
twisting could weaken the connection.... (unless twisted so much a
wire breaks).

It supposedly says on the package. I've never seen it.

Some wirenuts are apparently designed to do the twist while
you turn them on. Saves a little time/fuss for the electrician,
which is why they design them that way. It's remotely possible
that some wirenuts designed for "no pretwist" may (meaning
"probably only rarely") overtwist the wire if you pre-twist it
anyway.

It's best to do what the package says, and err on the side
of pre-twist if it doesn't say.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.