The point is that how does the whistleblower know whether or not they are not whistleblowing to the very people or allies to those being reported on if who is behind it?
To pull an example out of thin air, would you risk whistleblowing to TruthWave on Amazon if you knew that the Washington Post was running TruthWave?
Or, would you whistleblow on Tesla, if you knew any out of a hundred companies was behind it, like Meta, Alphabet, Amazon, ...? About the only "big" entity I MIGHT trust would be Berkshire Hathaway..
I think this trust (in the Post) is now misplaced, and in the case of the Post and Amazon, you absolutely shouldn't. But perhaps it always should have been with any single newspaper.
This is why whistleblowers now often work with two different organisations with different ownership/politics, or in different branches of media, or with a journalist backed by the ICIJ (e.g. the Mossack Fonseca leak investigation was shared with the ICIJ).
But yes, any generic online whistleblowing broker with dozens of concurrent cases is going to be such an obvious target for state or organised crime interference. Anyone making a business of brokering whistleblowing for a cut of the reward is an obvious risk.
Then the service seems to provide zero value, there are already “untrusted” platforms. If i have to anonymize myself anyways, i can just post on Reddit/Twitter/Orange site directy.