Whilst I think the deepfaking of his voice is ethically sketchy, they did at least a) get permission from the family and b) (apparently) only use it on words he had actually written (like emails, etc.)
(I say 'apparently' because whilst one use for it was confirmed as reading an email, the producer seems to be refusing to clarify where the other deepfaked audio is.)
There are a lot of affairs that get passed along to family (or others) after someone death. It would be completely inappropriate for family to close someone's bank account while they still lived; we have no qualms about their doing so after they've died.
Publishing yet-unpublished works is another example that this is only a step out two away from.
To add to this, when yet-unpublished works are published posthumously, they are commonly edited. For example, several of JRR Tolkien's works were edited for posthumous publication by his son Christopher. And even if the text is totally unchanged there must be choices about what to include and how to present it.
IMHO it's not at all strange for the family (particularly the offspring) of the deceased to make decisions, including creative/artistic/editorial decisions, about how their loved one's work and life are used and portrayed.
In Tolkien's case, that's not just obscure stuff. The Silmarillion is widely considered "canonical", but it was published after his death, with countless editorial choices by his son. In most cases, later writings explicitly contradict the ones Christopher chose.
He chose them because they were the ones most compatible with the other published works, because his father could never revise them. (Unlike The Hobbit, which as revised to make it more compatible with upcoming The Lord of the Rings.)
He was specifically chosen for the job by his father, who may not have agreed with the choices but was unequivocal that Christopher was the one to make them. Christopher himself has said that he'd change some decisions if he were to make them again, but that's true for any author.
To me, I'd just as soon The Silmarillion bear Chrisopher's name. Not as a matter of honor, but as a matter of clarity to fans who want to know what's "really" Tolkien.
Is this not general control of an estate? Seems entirely within what we in the West consider normal. Whether it's "creepy" or not doesn't really factor into all the other decisions made on the behalf of a deceased person.
permission to have your family decide to "deepfake" you should be opt-in. also, the whole point of "deepfake" is to falsely present an object as true. In a documentary, this is troubling. personally, every instance of deepfake should come with a on screen caption of "deepfake notice of creation of event".
The difficulty is going to be who represents the deceased if the estate agrees to allow the deep fake against the deceased's permission. It's both of a question of who has standing to sue the estate and who is going to fund the legal costs involved.
(I say 'apparently' because whilst one use for it was confirmed as reading an email, the producer seems to be refusing to clarify where the other deepfaked audio is.)