Bitcoin balance at the exchanges shows a different paradigm.

As per Glassnode's data https://studio.glassnode.com/metrics?a=BTC&m=distribution.BalanceExchanges on the Bitcoin balance at the exchanges, top has been reached in February 2020 with around 2,950,000 BTC and has been falling since to around 2,588,000 on September 26.

Mind you this data tracks not all exchanges but a set of majors. Whether that would be different from Chainalysis data or not is a different matter depending on their coverage.

As a secondary point, the chart you referred which also was used in the Coindesk article https://www.coindesk.com/first-mover-bitcoin-exchanges-cryptocurrencies-defi-hedge-fund-50-million has a misleading subtext.

It says that the highest number of Bitcoin inflow to exchanges (at 36,800 BTC) were reached on 22nd of September. That is not a cumulative number but a net change record for a day.

However, the net change in reverse i.e. net Bitcoin outflow from exchanges were reached couple of days before that as well when c. 20,000 BTC was moved out.

A more thorough and longer dated perspective can be found on Glassnode https://studio.glassnode.com/metrics?a=BTC&category=Entities&m=transactions.TransfersVolumeExchangesNet&s=1554094989&u=1601078400&zoom= here.

In summary, while the exchange deposited BTC figures are an important piece of information, cumulative figures are more relevant than single day changes.