[sbierwagen]

  I'm having trouble believing that it is [...] desirable

To make it less useful to build a NSA-style ASIC hash cracking cluster, like https://en.wikipedia.org/wiki/EFF_DES_cracker

  I'm having trouble believing that it is [...] achievable

The point is not to write an algorithm that is only fast on x86, rather than ARM, POWER, whatever; it's to write an algorithm that uses so much memory that it's not orders-of-magnitude faster to use an ASIC that's just a bunch of compute cores connected to fast buses, rather than a general-purpose processor with megabytes of on-chip cache.