Hi Alex! It is just the official term used for 'doublage'; the point being, many lay people think of 'dubbing' (of course originally 'doubling') as meaning 'dubbing into a foreign language' — but this is not inherently the case: it can in fact be voicing with (say) a different actor's voice in the original language (commonly done of course for the sung parts of musicals), with the original actor but a dialogue change — or of course with the original or a different actor into a foreign language.
In fact, almost all movies these days have most o all of their dialogue replaced, for purely technical reasons; nowadays, the term 're-voicing' is often used for this.
In this legal context, they clearly want to use the most all-embracing term covering these and any other possibilities, whence the use of this perhaps less familiar term.

AFAIK, it is all globally referred to as 'doublage' in FR — I am not aware of any different terminology used to express all these niceties.

I would avoid 'redoubler' as being something of a pleonasm.

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Note added at 3 hrs (2021-06-23 21:15:58 GMT)
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In one notable example, David Lean wanted to restore a lost scene from 'Lawrence of Arabia', but the sound negative had been lost; in the meantime, poor Jack Hawkins had lost his ability to speak — so his dialogue was magically replaced by another actor skilfully mimicking his distinctive voice.