[Old Lore]
Summoner's Rift is an artificial arena created by...summoners. For example, Baron, Dragon, Monsters, and Minions are all spell-casting constructs that don't have individual minds. So, it makes sense that the bushes are equally magical and effectively hide even a six-stack + Elixir of Ironed Cho'gath.
The Rift still isn't a physical place, and Summoners being replaced by entities beyond the fourth wall doesn't change anything. Magic is still a thing, bro.
And I am my own god, at least for now ;)
They got the champs backwards.