I guess it's more like 150 according to the studies in the second link. Anecdotally vocab acquisition is much faster in Esperanto due to the regularity and afix system, where learning a single new word root tends to give another dozen variants "for free".
By the way the second link is a critique of a single study, and it makes a pretty wild claim: "To see whether previous study of Esperanto would assist children in the subsequent learning of East-Asian languages (particularly Japanese)."
The claim that Eo helps French acquisition is much better supported from the links in the wikipedia article, considering the more similar grammars and vocabulary.
Most languages have some kind of derivational morphology that gives you variants "for free". The Wikipedia article on morphological derivation gives some examples for English: https://en.wikipedia.org/wiki/Morphological_derivation
I don't doubt that pre-existing knowledge of Esperanto helps with learning French due to the large number of cognates, but it's implausible it helps so much that you get "faster French acquisition after first learning Esperanto than learning French the whole time". Cognates would at best allow you to learn Esperanto + French in the same time it takes to learn French alone, but Esperanto isn't 100% Romance-based, so even that is unlikely.
In English getting the exceptions wrong ("I washed, I jumped, I readed, I runned, I eated, I writed") makes you sound like a child or an idiot (Ralf Wiggum from the Simpsons). In Esperanto, ending a word in "-e" makes it an adverb which means you can stick it on any root word to force adverbness. In English "-ly" makes something an adverb, except when it doesn't; "brolly" which is a noun, "fly" which is a noun, a verb, maybe an adjective, maybe sometimes an adverb ("fly-tipping"?), or "scaly" which is an adjective and doesn't become "scalyly" to make it an adverb. They aren't "for free" in English because you can't trust the pattern.
but it's implausible it helps so much that you get "faster French acquisition after first learning Esperanto than learning French the whole time"
I'm not convinced that it's true, but it surely is plausible; the other side of "can't trust the pattern" is that you can't easily see the pattern. Learning arithmetic then calculus seems better than trying to learn both at the same time; learning an instrument first then playing in an orchestra would be better than trying to join an orchestra and play with them while learning to play an instrument at all. People recommend beginners start with Python rather than 3D engine development in C++, or work on a model of an engine before they take a helicopter apart, right? Why not "learn European grammar rules in simple patterns" then "use that knowledge to climb faster through native languages which aren't so simple where the patterns are less clear"?
By the way the second link is a critique of a single study, and it makes a pretty wild claim: "To see whether previous study of Esperanto would assist children in the subsequent learning of East-Asian languages (particularly Japanese)."
The claim that Eo helps French acquisition is much better supported from the links in the wikipedia article, considering the more similar grammars and vocabulary.