Using Classic Outlook on Windows for personal email, calendar, and contact management
There is no good way to tell except the issue will stop reproducing. By tomorrow the change should be fully picked up by the client. If you see different, please let me know.
I just tested on my repro machine and my client has already picked up the change and I no longer repro the issue. It's probably the same for you if you restart Outlook and test (with reg key removed).
As and admin that uses patch management to delay updates for this exact scenario, how does one block a flight? KB and MS Office updates are not installed unless approved but somehow this seems to bypass that.