Meh. Even though they have the same name, the Arduino project is much bigger than the Arduino company. All things related to the Arduino project are welcome here. And in the case of the ESP32, many of the official boards actually have an ESP32 microcontroller in their WiFi modem.
But this question is not even specific to any one microcontroller. This is about C++.
From § 16.1 ¶4 of the C++11 standard:
After all replacements due to macro expansion and the defined unary operator
have been performed, all remaining identifiers and keywords, except for true and false, are replaced with the pp-number 0
So what that means is your conditional is equivalent to this:
#if 0 == 0