There was actually somewhat of a hidden feature late last year or maybe earlier this year - I don't remember which. But a user could go to their Playlist Edit page and simply click the Save button, and doing so would re-save the playlist and purge all the removed videos. That to me was sort of a cool feature - because it sort of like my kid ask me "Mama clean my room ! NOW !!!" so it was a two way street.
But then some people started complaining that YouTube picked up their room for them re-organized their toy box. And kids don't like that because they say - "Mama YOU moved all my toys and now I can't find nothing !!! Leave my toys alone and leave my room alone"....... Even though - what don't actually know is there is some very easy ways to get back the name of their toys and who gave them the toys. But kids these days - they are lazy and not willing to learn. ..... So - ow well .... they will get over it.... or else they won't. Mama has plenty of work to do just to keep them clothed and fed as it is.
But what you are asking .... with all due respect - is about the worst of both worlds - because you ask YouTube to clean your room and organize your toy box. And then leave you a note to say exactly what she did with your toys. If YouTube cleaned up every playlist 24/7/365 and then sent a email to every user who created a playlist and Mama tossed out some broken toy - then kids all over the world are gonna start complaining - "STOP PASTING NOTES ALL OVER MY WALL AND STAY OUT OF MY MESS OF A ROOM !!!
.... and they are right. It's your playlist - it's your responsibility to maintain it ;-)