I haven't read the article and I balked when they exclaimed the bit about 18 GB of RAM. That'd be an unusual number but, more importantly, is well below what I'd expect for a minimal amount of RAM in a designated 'professional' system.
These days, I'd want 64 GB as a minimum but I suppose 32 would suit for some tasks. I still muck about with some modeling that hasn't been shunted off to the GPU, so I'd even find a use for 128 GB.
A few browser tabs, email client, IDE, and Slack are going to eat up a goodly portion of 18 GB.
That is Video RAM for the GPU, though not the main RAM for the system. The minimum RAM amount you can buy the iMac Pro with is 32 GB, 64 GB and 128 GB configs are also available
Also, 18 GB was certainly a typo, if you look now, they are saying 16 GB now.