> are there platforms that actually use 58 bits?

The original article already contains a note that "Some more recent x64 CPUs use 5-level paging, which would increase this number to 57 bits [0]"

Apparently server-level "Sunny Cove" Intel CPUs implement this extension [1].

[0]: https://en.wikipedia.org/wiki/Intel_5-level_paging

[1]: <https://en.wikipedia.org/wiki/Sunny_Cove_(microarchitecture)>