You can find the explanation in this thread:
https://www.flyertalk.com/forum/chas...26-2018-a.html
There is a Federal regulation that limits the annual fee based on the
initial credit limit. Chase seems to have this implemented incorrectly, and their system sometimes refunds the fee if the credit limit is reduced. This happened regularly on Ritz accounts, but (as far as I recall) it seldom, if ever, occurred on other high-fee Chase cards. Based on the Ritz experience it shouldn't affect your ability to use the card for benefits, only for spending.