Earlier quoted context omitted.
They get a notification if they have chosen to receive notifications. It's not like the sender forces themselves upon someone else.
I think this and the other comments here show an important cultural difference: Western culture places more emphasis on personal responsibility: if you don't want to be disturbed, the expectation is that you turn off notifications. Japanese culture seems to be the opposite, in that you expect others to know you do not want to be disturbed, and thus you don't bother with turning off notifications.
And just the same, Japanese people are not one unified blob and each have their own preferences regarding texting, just like the rest of us.