That or he didn't notice or could have assumed the notice itself was one of many phishing attempts against large orgs.
If I saw a notification that my account was compromised by Pegasus I'd personally assume phishing.
PC viruses used to do that stuff going back so many years ago. Suppressing any notification under Windows, by disabling the AV software, its notifications, windows notifications related to it.
So it will amaze me that this is not done by any modern espionage software. Especially as the notification methods are known. Given that his device is hacked, that means a lot of avenues are under control of the espionage software. Even mails etc ... So impersonating the end user, to confirm they read a warning, is extreme easy.
I find it rather odd that people are so fixated on the idea if Kouloglou read it or not.
Its going to have every trick in the book (and outside it), to stay hidden. And it will have payloads to alter its behavior, updates, etc...
Nobody is going to pay you big fat money envelops for software that anybody can write in a afternoon. You want it to be as capable as ever, and you do not want it found!