I don't think that's a fair interpretation. They're not going on the attack, after all. Amazon's capitalization on ElasticSearch constitutes an existential threat to Elastic, not the other way around. Elastic is very much defending its existence, which, by the way, is the primary sponsor for the open source project. Moreover, the interpretation ignores that the "proprietary features" in question (including their source code) are available for free to the public.
I'm open to the idea that there were better (i.e., friendlier to open source) recourses available, but I'm not pursuaded by purist arguments that don't address the existential threat to Elastic and the ElasticSearch project.