The writer meant exactly what he wrote. Thats the reason you have to delegate UI updates from worker threads to the UI thread.
Re:The Dawn of Haiku OS
by icebraining on Sunday April 29, 2012 @07:14AM
(#3905707)
There can be many threads per process, but plenty of applications ("Generally") are still single-threaded or even if they aren't, they only use one for the UI.
I think the article writer meant "process" -- there are many threads per process, and that is present in most "contemporary operating systems". If this is their (Haiku Inc.'s) attempt at PR... they are not doing it well.