This is true. My statement only makes reference to the fact that this was also considered Hebrew tradition and Jude may not have been quoting a book that he carried around with him. I'm not arguing your point. Other writings are quoted as well...."Jasher"[Joshua 10:13] & [2 Samuel 1:18].
Of course he didn't have a book he carried around. But 11 copies were found in the dead sea scrolls that matched what was found in ethiopia in 4 of the 5 sections. I'm sure these scrolls were read in essene circles. This book also describes chasms such as the one Jesus described when speaking of Abrahams bossom. Jude treated it as scripture.