What it means
Google's account auto-delete can periodically remove older items from a selected activity category in My Activity. Browser history is a local or synced browser record and may remain even when account activity is deleted. Other Google activity controls can have their own retention settings.
A real-world example
A person sets Web & App Activity to auto-delete after a chosen period, then still sees recent URLs in Chrome's History menu. That does not necessarily mean the account setting failed.
What to do
Check the chosen account activity category and its retention period, then review the browser's own history controls if local traces matter. Save records you need before deleting them.
The distinction that matters
Auto-delete acts on the selected control over time; a manual deletion can remove selected activity now. Google notes that browser activity might be stored separately and that settings are changing for some Search services.
Google's account activity guidance Google's My Activity overview
