https://github.com/bitcoin/bitcoin/blob/d72758c3f6c34cd835f5de3efc230964f3b1ea56/src/torcontrol.cpp#L539

If a user is running Tor proxy outside localhost (perhaps on other host inside LAN or in containerised environment) , the automatic creation of onion services ends up creating an onion service listening to hardcored 127.0.0.1 address on the Tor proxy's host instead of the private address of the bitcoind – effectively running an empty onion service listening the Tor proxy's localhost.
if (j == 3 && value[i] > '3') {
                            j--;
                        }
                        escaped_value.push_back(strtol(value.substr(i, j).c_str(), nullptr, 8));
                        
                        i += j - 1;
                    } else {
                        escaped_value.push_back(value[i]);
                    }
                } else {
                    escaped_value.push_back(value[i]);
                }
            }
            value = escaped_value;
        } else { 
            while (ptr < s.size() && s[ptr] != ' ') {
                value.push_back(s[ptr]);
                ++ptr;
            }
        }
        if (ptr < s.size() && s[ptr] == ' ')
            ++ptr; 
        mapping[key] = value;
    }
    return mapping;
}
/** Read full contents of a file and return them in a std::string.
 * Returns a pair <status, string>.
 * If an error occurred, status will be false, otherwise status will be true and the data will be returned in string.