Good catch. "English" should read "Germanic", also they left out the Balto-Slavic Lingustic subfamily, ,more distantly related to the other four, but still an Indo-European language, like the Iranian languages, Sanskrit and it modern descedants Hindi, etc, ancient Hittite and the Anatolic Language related to it, Armenian, and Tocharian, an extinct language spoken in Central Asia by a long dead people who looked European.
I think the journalist had an imprecise grasp of language classifications. Indo-European is a "Language Family". It is broken down into 12 "Branches". Of those 12, four are: Celtic, Latin, Hellenic (Greek), and Germanic. The Germanic branch is then broken down into "Languages", one of which is English.
Saying that Indo-European led to Celtic, Latin, Greek, and English is not wrong, but it's sloppy and (I feel) a bit misleading -- since it lumps English in with Language Branches and makes English seem a bit more significant than it is (some the standpoint of linguistic history/genealogy).
It's also incomplete, since, as you point out, there are many other branches and languages that are not mentioned at all. Again, it is not "wrong" to provide an incomplete list of what Indo-European led to, but it is perhaps a bit misleading.