I have no strong opinions on the topic, but the author sounds like an asshole going for the impression that confidence == competence.
If, as you suggest, AWS is Amazon’s profit-center and Amazon.com is their loss-leader, that’s another point in the OP’s favour arguing that AWS isn’t killing your AWS-competitor business. (Because AWS would have to make money, if it were to be used to prop up Amazon.com; so they would not be unfairly dumping AWS prices to outcompete your AWS-adjacent business.)
This article is a bit silly.
Bold claim and the main point of the blog post but you never expand on why.
From the outside and to many people I speak with, it looks like Amazon just grabs popular open source packages with permissive licenses and then starts selling it.
I hope more open source projects add in clauses that protect themselves from these monstrous corporations.