They go over the effects of compression - which they say only degrades the protection - but at the same time also degrades the identification accuracy of the AI model.
So if your crappy 6 megapixel camera cannot take a clear shot of the cloaked pixels - or effectively applying a blur filter - would also affect the AI detection.
They are lucky in this case because compression does defeat the cloak to some degree— However, compression at those levels also defeats the ability of Facebook to accurate identify you.