The 1MB is likely referring to the SPI flash device that the ESP-01 modules use. Many of the other boards feature larger SPI flash chips up to 4MB, and I belie

The 1MB is likely referring to the SPI flash device that the ESP-01 modules use. Many of the other boards feature larger SPI flash chips up to 4MB, and I believe it's possible in theory to boot of an SD card with them too if you remove the flash chip.