Yes, I found that out the hard way. In my earlier tests, I did KBT first then to a brief (5 minutes) wash, then KRST. The brown toner REALLY took off in KRST! It shifted all the way to almost bright orangy brown in about 30 seconds. Since then, when doing KBT first, I either use HCA and 30 minutes wash or 60 minutes wash without HCA.
Doing KRST first, 5 minutes wash seems to be sufficient. Longer wash didn't change the result. (of course, my final wash is long for archival reasons)