[lmm]

That seemed to match the lightbluetouchpaper description - the "hack chip" goes where the optional legacy (non-quad) SPI chip would go.

[xevb3k]

Given the size estimation, it wouldn’t cover the whole footprint.

But... why put it on an unpopulated footprint. Why not just replace the original Quad SPI IC with a backdoored device?

[lmm]

What do you then do when they upgrade/change the Quad SPI IC? A separate chip means a stable interface they can conform to.