Saying something also helps a lot - for E2EE the middle means nothing at all. The risk is on the end device and the metadata collection. How would cloud affect E2EE? Even Cloudflare only breaks SSL - if the content is encrypted on device, it stays that way to the other side.
Discussion
If you dont understand a text, that you read, I cant help you anymore!
No I think you need to read a bit wider than one report. If you read wider, would not have to keep trying to explain it. Just read WhatsApp's T&Cs here at https://www.whatsapp.com/legal/terms-of-service under Affiliated Companies and sharing of information (that is metadata). This is active sharing.
Then you can read Signal's policy at https://signal.org/legal/ and you'll see "Signal does not sell, rent or monetise your personal data or content in any way – ever".
As I said it is chalk and cheese here on data sharing. The one actively shares and monetises metadata, the other explicitly does not do so.
That is why I replied to you and said yes there is a very big difference between WhatsApp and Signal, and you cannot just lump them under the same privacy levels.
If you'd done the reading on the T&C's like you expected me to do the reading, you would have seen this quite clearly.
If you read up on proper E2EE that is initiated at the end user device, you'll see too the whole point of that is that the message content is not seen or decrypted in any way by any cloud service, so what cloud service is used is irrelevant. The only exception is a service hosted with its SSL via Cloudflare, then Cloudflare does break that SSL encryption in the middle. But that is not how WhatsApp or Signal work, as they both use the Signal protocol.
Both Signal and WhatsApp have been independently audited (by the EFF for WhatsApp, and Signal by independent auditors from Germany, Switzerland, the USA and Canada). Those all confirmed the content of messages are secure irrespective of the clouds they use.
The difference comes in the metadata side, which I explained earlier from both their written T&Cs. The metadata is also what is available, and what can legally be subpoenaed to be handed over to a country's law enforcement so how much is stored, is also important, but in the case of WhatsApp they actively share that anyway to partners (you can read about how that happened via Facebook and the Cambridge Analytica scandal). Facebook was of course now the Meta that WhatsApp refers to in their T&C's and was one reason why they switched the name of the holding company away from Facebook. But that is another whole story.