It is difficult to determine the exact amount of Bitcoin held by centralized exchanges, as this information is not always publicly disclosed and can fluctuate over time due to market conditions, trading activity, and other factors.

That being said, it is possible that some well-known centralized exchanges such as Coinbase and Binance do not hold a significant amount of Bitcoin, relative to the total amount of Bitcoin in circulation. This is because centralized exchanges typically hold Bitcoin in order to facilitate trades and exchanges for their users, but they do not necessarily need to hold a large amount of Bitcoin at any given time in order to do so.

Additionally, centralized exchanges may hold other cryptocurrencies, such as altcoins or stablecoins, which can be used to facilitate trades and exchanges on their platform. These other cryptocurrencies may account for a larger percentage of the exchange's total holdings, relative to Bitcoin.

Overall, while it may be true that certain centralized exchanges do not hold a large amount of Bitcoin, the exact amount and distribution of Bitcoin held by these exchanges can vary widely and may be difficult to determine with accuracy. As such, it is important for individuals to carefully assess the reputation, security, and reliability of any exchange before using it to trade or exchange their digital assets.