Bitcoin has an order of magnitude more hashpower than some other coins mined with the same SHA256 algorithm, like Bitcoin Cash and Digibyte, so Bitcoin is relatively safe.
The notice explains that the 51 percent attack did not occur because there was something inherently wrong with the Bitcoin Gold blockchain. It clarifies that a bad actor who manages to control the majority of a blockchain’s hashpower power could theoretically launch 51 percent attack, even on Bitcoin’s blockchain.