Jarvan Cataclysm double bug?

ACTIVE: Jarvan IV dashes to the target enemy champion, dealing them physical damage and becoming immune to crowd control during the dash. Upon impact, he creates a circle of impassable terrain for 3.5 seconds that grants Sight icon sight around it.

so ,immune to cc ,but you can get knocked up /back by lee sin at very least said ,and creates impassable terrain but coded as minion? vayne can condemn into ur own ult ,but she can dash away ? ghost summoner spell can also get you out ?

this bug is like you could dash away from morgana root or ryze root bad coding ? enlighten me pls IMPASSABLE ,NOT SEMI PASSABLE