Why would you assume that security researchers don't know about these? If anything, wouldn't all the bad press and scandals make WhatsApp a more likely target of scrutiny?
> And most importantly, most security researchers lack the money and power to fend off the legal consequences of these acts.
Yes, security research is generally expensive, but do you have any evidence for Meta taking legal steps against it and making it actively harder? I remember e.g. the controversy around WhatsApp re-encrypting unconfirmed outbound messages to a new key; this was revealed by security researchers and widely discussed. (Not that they're making it easier by providing source code for WhatsApp's cryptography or a debug interface to validate what's actually going on in the client, but neither does e.g. iMessage.)
In fact, there's a relatively absurd lawsuit against Meta on WhatsApp encryption going on right now, and these claims are widely being repeated all over social media.
It's not that Meta is making it harder to report them but the fact that reporting them does not meaningfully disincentivise Meta from carrying on with their unethical behaviour (i.e. it is not an effective deterrent).