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For that reason, the usual trick is to use asymmetric encryption to protect a symmetric key (a fresh one per payload) that is then used for the actual payload. That way you get the speed of symmetric encryption with the benefits of asymmetric ones. (Though evidently that's not what the PS5 uses here, otherwise it would be useless to read out one symmetric key).

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As your sibling post technically notes, asymmetric vs symmetric is a wash, here. To use asymmetric encryption for saves, the PS5 would need to know the public and private keys, so you would be able to extract those and still have the same access.

Of course, there are still advantages to having the symmetric key not be used as is, but there are many solutions other than asymmetric encryption.

And to add to that: you should use as many different symmetric keys as possible as long as asymmetric decryption of the key doesn't overly degrade performance.

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