Do you think it's the interrupting that's the issue here, or the fact that they're changing the subject? (and hence, not listening to you)
I think both "wait" and "interrupt" culture etiquettes involve supporting the current conversation, not ignoring the other person's input. The latter is frustrating in both styles.
Being from a wait culture, I find it mildly rude to also interrupt in an agreement, even if for a very short acknowledgement. It's an interruption after all.
I don't mind in a work setting or with acquaintances as I know lot of people are interrupters, but now I realize I do expect my friends and partner to let me finish uninterrupted. So it's clearly still a rudeness flag for me.
I think both "wait" and "interrupt" culture etiquettes involve supporting the current conversation, not ignoring the other person's input. The latter is frustrating in both styles.