I know this because the bootrom writes to this area CONSTANTLY, mostly using it as stack space. A QEMU fork that emulates the iPhone 2G also has SRAM here (https://github.com/winocm/QEMU-s5l89xx-port/blob/master/hw/iphone2g.c#L591) as does my emulator, PurpleSapphire (https://github.com/PurpleEmu/PurpleSapphire)
I know this because the bootrom writes to this area CONSTANTLY, mostly using it as stack space. A QEMU fork that emulates the iPhone 2G also has SRAM here (https://github.com/winocm/QEMU-s5l89xx-port/blob/master/hw/iphone2g.c#L591) as does my emulator, PurpleSapphire (https://github.com/PurpleEmu/PurpleSapphire)