This apparent contradiction is just a moderately clever way of using an ambiguity in the word.
If "deplatforming" is taken to mean "depriving people of an easy means to find and communicate to an audience" it can be an effective technique depending on context, alternative communication channels, etc.
If "deplatforming" is taken to mean "a novel social ill based on depriving people of their right to communicate" then yeah it's a myth.
If "deplatforming" is taken to mean "depriving people of an easy means to find and communicate to an audience" it can be an effective technique depending on context, alternative communication channels, etc.
If "deplatforming" is taken to mean "a novel social ill based on depriving people of their right to communicate" then yeah it's a myth.