DFU for STM32L optimized to not program pages containing 0x00?

[MSipo]

As the STM32L flash is erased the memory cells are set to 0x00 (not 0xFF). Is there a DFU tool that can optimize firmware upgrade that skips programming of blocks already containing 0x00? The DfuSe Demo only has "Optimize Upgrade duration (Remove some FFs)".

[TDK]

STM32CubeProgrammer can perform a DFU upgrade as well. It is more recent and may have features you're requesting.

Does the STM32L flash really erase to 0x00 and not 0xFF? Is it a different type of flash than all the other ST chips?