Replacing one copy with another in your own device is a fairly intrusive act.

We don't have a word for it yet, given that classical censorship developed in the era of printed books, when such activities were technologically impossible. But I would say that it falls under penumbra of censorship because of the intent. And the intent is to remove certain speech from average reader's view without the reader's consent.

Censorship does not have to be total in order to be censorship. Even in authoritarian states, small oppositional media outlets may be tolerated, so that foreign accusations of media control can be rebuked: "Hey, look at Radio X, we are definitely not censoring them." But their reach is carefully kept limited.