TL;DR adding a compromised source of entropy to a pool of already secure sources of entropy can catastrophically compromise the final result.
It's better to source entropy from a smaller number of harder-to-compromise sources.
That's why I like the iterated hashes method; the security surface area is both very small and highly likely to be well tested.
https://blog.cr.yp.to/20140205-entropy.html
TL;DR adding a compromised source of entropy to a pool of already secure sources of entropy can catastrophically compromise the final result.
It's better to source entropy from a smaller number of harder-to-compromise sources. That's why I like the iterated hashes method; the security surface area is both very small and highly likely to be well tested.