They should be saying it for two reasons.
One, they should actually do it, it’ll be very popular, and it’s the morally correct thing to do.
Two, whether or not they actually do it when they get power, if they want to win (very questionable) it is a good strategy that people will like and will get them votes.
The same reasons Kamala should’ve called out Biden’s inaction on Gaza. Yes you should actually follow through on your campaign promises but also even if you don’t plan to you should lie, you’re a politician, that’s the job.