Actually only you have. No one else has. A few actually backed me up. I even already talked to APR directly. Surprisingly they haven't chimed in here after I sent him the link. Maybe he doesn't want too.
And flash ram must have spare space to overwrite or it won't allow it. That is a given.
No everyone who has chimed in about flash memory has verified that once a sector is overwritten then it is lost. Which is what you claimed was not possible.
The information you provided, which i stated well before you did only says that in the case of flash storage memory like a usb drive or an SSD that it will write to the next block to make sure that the information on the previous block is recoverable. Also since depending on the type of device there is a limited number of write cycled this prolongs the life of the device.
In the case of these ecus there is no address system in the OS that says ok the timing map was in A000D last time but since we have overwritten it again its now in A0000E just to make sure we dont lose the data.
The Data is erased from A0000D and it puts the information back in A0000D not A0000E. since it does this the data that was there previously is erased.
Since not all of the space is used for relevant data in the flash memory that actually runs the cars that is what people use to add in what they need for switching (in some applications). That data maybe filled with 0s originally and later it has actual information. Since that space is changed the checksums total changes and this is what VW is using to detect the modified software in the vehicle. Due to the fact that with every update and flash the various spaces of data that are used may change as they modify maps and make changes to say emissions controls when flashing you MUST rewrite all of it even if you are putting 0s back where 0s were and 1s back where 1s where. When we flash a car back to stock to ensure that the file does not end up corrupt and so that the checksums are correct and stock we again write back over those same spaces.
This is not a CF card in your camera that is using the blocks sequentially in order to prolong the life and preserve data. The data is put back to exactly the same block it was before or if it is moved 0s are put where it was before.