The reason for the different addresses generated by TonHub, TonKeeper, and wallet.ton.org when using the same mnemonic phrase is because the address depends on the wallet contract version being used.
It is important to note that v4 of the wallet contract allows for the installation of plugins, which could potentially introduce security vulnerabilities if used improperly. If you do not require the advanced features provided by v4, it is recommended that you use v3 instead.
Additionally, it is important to exercise caution when using web wallets, as they can be vulnerable to attacks. Recently, there have been reports of a site called wallet-ton.org that appeared to be a web wallet, but was actually designed to steal passwords and empty user accounts. Web wallets are considered "hot wallets" and should be used with caution. It is recommended that web wallets include better security features to protect users from potential attacks.