In my opinion, the phrase "based on" implies that a lot of the Elasticsearch functionality is actually Lucene functionality. I disagree that this is the case, I think there is a lot of functionality that Elasticsearch brings that is really othogonal to the Lucene project (sharding, multi-tenancy of indexes, clustering, managing nodes, etc.) Again, you my opinion, definitely enough for it's own project.
If that isn't what you meant then perhaps we are in agreement. :-)
Since you have mentioned this I have read three more articles and short blurbs about this kerfuffle and _they all_ have used the same "based on Lucene" text when describing Elasticsearch. As you say, Wikipedia seems to be the one true source of this phrasing!
If that isn't what you meant then perhaps we are in agreement. :-)