There’s a lot of factors to consider, though. Many rendering packages incorporate a “low priority” feature which will have the rendering job ease up a bit if the user is trying to do other things. Other packages let you set aside whole cores during rendering. (This is a tick in the “RAM doesn’t matter” checkbox.)
However if s/he gets into motion graphics or any poly modeling, there are plenty of functions which utilize RAM. Video rendering, dynamics simulation, retopologizing, all use RAM. (This is a tick in the “RAM does indeed matter” checkbox.)
But, really, RAM is so cheap, there’s nothing wrong with erring on the beefy side. 32GB is crazy but not as crazy as a $3600 laptop (I KID).
Lastly, a beastly enough computer will remain entirely usable while rendering. Having a properly cooled desktop instead of a groin-melting laptop will definitely help.