Can someone please provide a clear explanation to the February CookOff question MIXFLVOR?

The editorial for the problem is written in very bad English and I find it difficult to understand what the author is trying to communicate to the reader. Can someone who understood whatever he wanted to say please provide a clear explanation. Thank you very much!!

I have understood the 2 lemmas. After that, whatever he is trying to say in Supporting Deleting latest-added element onwards is just going over my head cuz he thinks he wrote it in English, but it aint English. @kingofnumbers, ask some grammar verifier to rewrite that part out man please for the benefit of mankind