Why does asterisk only work in one of the two cases?

Question

Asterisk

This is how it works:

[incoming]
exten => _7XXXXXXXXXX,1,Answer()
exten => _7XXXXXXXXXX,n,Playback(hello-world)
exten => _7XXXXXXXXXX,n,Hangup()

It doesn't work like this:

[incoming]
exten => s,1,Answer()
exten => s,n,Playback(hello-world)
exten => s,n,Hangup()

Answer 1

"s" is a special extension
that gets it in certain configurations, but not always
"_." - universal