It's always funny to me how the go-to examples of like, "See, they just blindly support anything the regime does!" tend to be relatively minor events after the state in question has considerably chilled out. Like, Stalin and Mao did much worse things compared to Khrushchev/Hungary and Deng/Tienanmen. The problem being, communists are generally willing to criticize things like the Great Leap Forward, because, surprise surprise, we don't just blindly support anything they do. The reason for this is that the word tankie isn't meant to describe someone who blindly supports everything a communist country does, as it's claimed to, but rather, someone who supports anything any communist country does.
The fear Western leftists had that led to the phrase being coined was that people who had previously been critical of Stalin and Mao would respond positively to the countries moving away from their approach, and so they had to create a label to discredit such people and associate them with the previous leaders. It's one of the reasons Khrushchev's approach was questionable, because no matter how much you try to distance yourself from someone like Stalin and paint yourself as "one of the good ones," you're still never going to appease the Western left that demands absolute perfection, let alone the West in general.