Sorry it took a while to reply. My computer and all it's contents went out for a very long lunch break.
No it's not inherited in the pure sense of the word. It's a Microsoft addition. Sometimes vendor specific additions are intended to make software more vendor and platform dependent. This particular thing is more of a practical addition when the XML standard is confronted with the real world. It essentially, allows the download to continue, but also returning control to the program rather than waiting for the download to complete. Just imagine a modem and a 5Mb download page. > 7secs, and the browser will surf elsewhere :) I have not included it in class structures because it flies in the face of perfection and XML genericism. But the script might be odd without it. This book is brief intentionally, with few cases of "going off at a tangent". So in the interests of not expecting you to read a 1500 page book, which would personally make me fall asleep with all it's detail, I left some things up to the reader. :)
Why would false catch more than one error? I don't see why. Perhaps true would ignore something but no that I have seen. Is there anything specific you have found? I would be interested to know. Thanks.