Based on my research, the frequency of updates for a NASDAQ-listed company is as follows:
Annual Reports and Proxy Statements: These documents are updated annually and include information about the largest shareholders.
Quarterly Updates: Some companies may provide updates in their quarterly reports (10-Q filings) or earnings reports.
On Request: Companies are not legally obliged to provide an updated top 20 shareholder list upon request by a shareholder outside of these regular reporting periods.
So I guess we won't get to know it.