I think people just copy the information from the vendor there and they say 520KByte RAM, which is technically true but as you’ve already said it’s split into IRAM and DRAM (also discussed in Available SRAM in ESP-WROOM32). Some board definitions are merged from external pull-requests (example).
The only two boards listed as 520Kbyte are AZ-Delivery ESP-32 Dev Kit C V4 and the M5Stack GREY ESP32.
The latter contains, per schematics, a ESP32-D0WDQ6 chip, which in its datasheet states a 520KByte total SRAM. Pretty much all the other boards with that chip are listed as 320KByte in PlatformIO, refering to their DRAM. So, it’s just for a board definition error in those 2 (of 76 total) I think. boards
→ Issue to Issues · platformio/platform-espressif32 · GitHub or PR there would be good so that devs can address this.