You're correct that this "creative re-application of cultural standards", along the lines of Dante / Virgil, is what's going on here.
There are some key differences. For one thing, Virgil and everyone who knew him personally had been dead for 1500 years, while David Attenborough is still alive, and those who know him personally will live for another 50 years. For another, it was absolutely clear to everyone that Virgil didn't actually say the things Dante put in his mouth; whereas as deepfakes improve, it will be more likely that people think David Attenborough actually did say whatever has been put into his mouth with a deepfake.
The whole thing's a mess. It'd be hard to draw a bright line between the crazy bullshit medievals* literally believed about Virgil, and the poetic, metaphorical bullshit Dante wrote about him.
(*I actually had a Latin professor in the 21st century sincerely advocate that Eclogues interpretation. There's a mode of thinking behind this stuff that, to put it tactfully, confounds people about what's the difference between fiction and reality).
There are some key differences. For one thing, Virgil and everyone who knew him personally had been dead for 1500 years, while David Attenborough is still alive, and those who know him personally will live for another 50 years. For another, it was absolutely clear to everyone that Virgil didn't actually say the things Dante put in his mouth; whereas as deepfakes improve, it will be more likely that people think David Attenborough actually did say whatever has been put into his mouth with a deepfake.