I think because the big failing before was that Zoom was using AES, but was using it in ECB mode. Zoom clearly paid near-zero attention to security until recent

I think because the big failing before was that Zoom was using AES, but was using it in ECB mode. Zoom clearly paid near-zero attention to security until recently. So by saying “GCM encryption” they’re highlighting that the fixed the mode by which they are using AES encryption.