SUSE originated in Germany, where it’s just the normal pronunciation. “Suse” also pre-existed as a nickname for “Susanne” (of course, the company name was derived from an acronym which isn’t used anymore).

The issue comes in when non-Germans, especially English-language natives try to pronounce the word. English pronunciation is incredibly inconsistent. Hence English speakers tend to fail (very confidently) when pronouncing foreign-language words.

(Fwiw, Germans and many others don’t know anything about the silent G in “gnome” and will happily pronounce GNOME the way the project intends without being told. Similar things are true for the I in Linux.)