I nominateトクリュウ for a yet-to-be-established award for Japanese terms that need not be rendered—and are best not rendered—in kana.
Neither of the two characters of the Japanese expression 匿流, the abbreviation of the term 匿名・流動型犯罪グループ would be difficult to understand if left as kanji. Both are taught during the mandatory schooling years in Japan, and both kanji conjure up understandable meanings, not because they are “ideograms,” but because they are logograms used in other common expressions. One is 匿名, meaning anonymous, and the other, 流動 means flow or fluid. Both these characters are constituent parts of the longer, proper expression.
Is abbreviation called for? Perhaps. But there’s no need for kana, I think, since people not familiar with the proper original expression might not understand it, and that undermines the purpose of the communication, unless the purpose is to demonstrate the desire of the communicator to appear trendy.
The representation of this expression in kana might seem trendy, but it hides the terms behind the abbreviation. My guess is that many native Japanese speakers are not yet familiar with the proper underlying expression—quite similar to the situation with the Japanese term SNS (which I will discuss at another time)—and many probably could not provide a proper explanation of the term, beyond being able to either link the kana expression to specific recent crimes or generically describe types of associated crimes, nicknames of criminals, or places such as Myanmar or the Philippines from encountering the term in crime news coverage recently.
This trend to abbreviate in Japanese can get out of hand. It is sometimes useful, but when it combines with kanaization, it can fail to help even native Japanese speakers understand what is meant.