I mean the plum blossoms appear as long their techniques are performed perfectly with the concept/theory. unlike what others believed only certain techniques can perform it, all Mt Hua techniques can actually let plum blossoms appear, even the basic ones. Chung Myung used a basic technique to make it blossom before. So it's not like he suddenly brought up a lost technique, it was more like he understood or comprehended the original techniques very well.
Not really. The first time he showed his blossoms was during the watchamacallit contest with zongnan. They recognized the stance. And one of the elders even panicked that he shouldn't be using the technique if he hasn't mastered it. He did all the falling petals. The pallicide. The cleave. 7 blossom blade. And since then he'd been performing more styles in his fights. Naturally, it should have been in their minds that chungmyung knows more than all of them combined

Wait... they already saw chungmyung doing a bunch of styles where he summoned plum blossom petals even before the other disciples could (and without being taught at that). How come they didn't think that he might know the technique as well?