If you actually read their paper, you will find that it's only the sign of the correlation that is being questioned. The field has generally been aware of this interpretational gap, and that's why two-sided hypothesis tests are important. Cellular neuroscience and electrophysiology are only starting to face the challenges that fMRI faced 2 decades ago.

To me this is like shitting on cars in 1925 because they kill people every now and then. Cars didn't go away, and nor will fMRI, until someone finds a better way to measure living people's brains.

TUM's press is being sloppy, from conflating fMRI with MRI to presuming this is revolutionary, and ignoring earlier empirical work against this narrative (Windkessel's, Logothetis beta/gamma coupling, etc.)