Nope, IB does charge you on idle EUR and CHF cash balance above 100k, it has been going on for a while. I had quite a bit of EUR cash sitting in an IB account when that started, and decided to invest and exchange the euros to avoid the charge, and from memory in 2017 it wasn't a great idea. Still get charged once in a while when I keep the balance over 100k, moving back to Europe soon, might keep some euros cash in the new bank there.
https://www.interactivebrokers.com.hk/en/index.php?f=1595
check " Interest Paid on Idle Cash Balances " in the link above.