Of course these orgs have their own infra monitoring, but technically anybody can monitor them and then claim to do so.
(If these companies signed up for the service then or course it would be legal to claim that.)
This company (is there a company behind it, I couldn't find those details) markets to countries outside of Israel I assume.
I hear what you are saying about the credibility hit I'm taking with showing logos like this. Will think what to do about it!
As for myself I turn down every request for a logo, I like and use your product but I don't really care if you cut me a small break for using it.
I have now changed this to include only logos of companies with whom I am directly involved, who are actively using my service to monitor their SSL certificates, and who have agreed to have their logos appear on my landing page.