Whistleblower protections, where they exist, a) don't guarantee that they are applied fairly, b) tend to come with all kinds of "did you do the proper process" restrictions and c) apply to specific groups of people (i.e. people speaking about things they legitimately become aware of due to their work). It very easily squares that whistleblower protections exist and at the same time they want to limit their use and come down hard on anyone falling outside of them. (Some details on how it works in US national security: https://en.wikipedia.org/wiki/Whistleblower_protection_in_th... note fun parts like "needs to escalate internally" while at the same time "internal retaliation isn't forbidden and can't be sued against")

People like Assange aren't whistleblowers, so those protections don't apply to them.