Tom it is mathematically derived. That makes it as hard and physical as any other law, as far as I would care. The reason platforms often dispute it in favor of Reede's law, is to try to justify profits being drawn by network clustering (creating social bubbles), which reduces network maintenance cost, but also network utility by Metcalfe's law, increasing profit, whilst arguably leading eventually to atrocity, which maybe warrants the negative Metcalfe utility you mention.

Platforms are a profit driven utilisation, remove those, and full Metcalfe utility (thus also value), again appears.

This is why I argue all networks should be solar powered, as with that the network can be self funded by Kardashev money, so no longer any need for platforms to carve up the network into bubbles to increase profits.