- Anyone know why it omits English?
No website reports common or non-shared segments of arbitrary multiple languages, relative to some database. You can get certain multi-language comparisons from the Frankfurt interface by including a Language Class entry, but you couldn't select e.g. just 3 Chadic languages. You also can't get non-shared segments. For that you would have to do the computations yourself on the UPSID database. There are numerous discussed interfaces in journal articles or former / broken interfaces: the Frankfurt one seems to be the only functioning interface.
The omission of English is a consequence of "the quota rule". To quote from Maddieson's book
The languages included in UPSID have been chosen to approximate a properly constructed quota sample on a genetic basis of the world's extant languages. The quota rule is that only one language may be included from each small family grouping, for example, among the Germanic languages, one is included from West Germanic and one from North Germanic (East Germanic, being extinct and insufficiently documented for a reliable phonological analysis to be made, is not included).
German was selected, therefore English was not selected. There is no discussion of why specific languages were selected.