I agree with what you say, but the blog post you linked is
hugely misleading. (remember, it's the OSI blog, of course they are going to twist it for their goals) The court did not affirm that "calling your non-OSI-approved licence open source is false advertising".
As in the judgement:
"It is undisputed that Defendants made the statements at issue to convince customers to adopt ONgDB over Neo4j EE. Because Defendants misrepresented ONgDB as a free version of Neo4j EE licensed under the APGL, there is no doubt that this price differential (free versus paid) was likely to influence customers purchasing decisions. See Hinojos v. Kohl’s Corp., 718 F.3d 1098, 1106–1107 (9th Cir. 2013), as amended on denial of reh’g and reh’g en banc (July 8, 2013) (recognizing under the UCL that price is material to purchasing decisions). Thus, the Court finds that Defendants’ statements suggesting that customers could obtain a “free and open source drop in replacement” for Neo4j EE were material."
What the court did affirm is that the upstream licence was a modified AGPL with additional restrictions. The defendant has stripped those restrictions (claiming the AGPL "you may remove" clause allowed them to) and distributed the product as "free and open source". This was false advertising as they were not capable of stripping the Commons Clause and the copyright identification.
Notably, this does not mean that it's false advertising to claim your software is "open source" when it is not OSI-approved, it means that if you offer a modified version of a piece of software, you can't advertise it as "free and open source" when the forked version is still bound by the Commons Clause prohibiting selling it in any way.