I haven't worked at either... but I did work at a regional retail company.

Walmart is a massive logistics company that dwarfs any other - save maybe Amazon (and it would be interesting to see the break down side by side).

I believe it is dangerous to put the FAANG companies on such a pedestal.

Consider even McDonalds Tech Labs - which sold to IBM which was doing some rather interesting things with machine learning, and bilingual natural language processing (drive throughs).

My point is one of "Walmart to Google is likely much less of a jump than people imagine... other than the name attached."

https://en.wikipedia.org/wiki/Walmart_Labs