Are you sure because i remember that Polonix had created fancy bit coin addresses. And more likely it was a big holder transferring or withdrawing from poloniex.
1Po1oWkD2LmodfkBYiAktwh76vkF93LKnh - 10,762,473 - Poloniex cold storage
The cold storage addresses from the old exchanges were in 2020
1DUb2YYbQA1jjaNYzVXLZ7ZioEhLXtbUru - 25,796,703 - Bittrx cold storage
1Po1oWkD2LmodfkBYiAktwh76vkF93LKnh - 10,762,473 - Poloniex cold storage
14quvdxXj7h4kcfhhuKX39wRc6X5sodkjM - 1,368,587 - Hitbtc cold storage
1K1wA1v9CwDY8LKjjHeDaUWCnfWBzuqLfg - 118,160 - Hitbtc hot storage
Assuming people with upto 1/2 million (or more) are not storing in multiple addresses like 50K each