GA4 now includes a warning system for '(not set)' values, marked by an exclamation icon. The tooltip suggests changes may take 24-48 hours to reflect in reports and recommends users address the '(not set)' data to improve attribution.
However, this warning raises concerns about confusion and false expectations, as '(not set)' values often stem from issues within the tool itself, highlighting larger ongoing problems with session tracking in GA4.