Its pretty much set in stone. https://www.newsweek.com/kamala-harris-tim-walz-cnn-interview-watch-election-1945198
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Tuesday evening, CNN revealed that it had secured the first sit-down with Harris, a joint interview with her running mate Minnesota governor Tim Walz conducted by anchor Dana Bash. The interview will air Thursday at 9PM
https://nymag.com/intelligencer/article/when-will-kamala-harris-sit-for-an-interview.html
the campaign was consistently saying they were doing an interview before the month was up.
Where were you seeing that? The quote I consistently saw was that she would schedule an interview before the end of the month. E.g. https://www.newsweek.com/kamala-harris-gives-update-interview-plans-1936779
"I've talked to my team, I want to get an interview scheduled before the end of the month"
Which seems intentionally phrased to offer some wiggle room. (And AFAIK, this is the quote that people keep referring to, which was back on August 8th, so it's not like it's a lock that the schedule wouldn't change over the chaotic next few weeks).
The market was too low sure but you didn't have to distrust Kamala or think she was scared of interviewing or anything to think it might be NO. It wouldn't have been that weird for them to announce that it was next week.
I like to watch interviews directly. I used this to decide to bet yes: https://www.foxnews.com/video/6360994031112