Monty Haul character generation in new editions?

I've read about newer Dungeons & Dragons (D&D) dice rolling methods for
character generation for ability scores, but now there's one using 5D6?! 
Maybe roll five and drop two?  How is it anything other than Monty Haul?!

Maybe it's only option if Dungeon Master (DM) wants more powerful
characters, like 'epic level campaigns' (never used that, but 36 levels)?

How could DM deal with this without unbalancing?

I guess since /Immortals Rules/ (and /Wrath of The Immortals/) it's
possible to run games with much more powerful characters, but DMs might
need more experience to do so.

When we were 12, my DM said 'keep rolling' until I got one or more 18s. 
Maybe he didn't know how to balance game--because he was 12.  However,
when official D&D book says do something this level of 'Monty Hall' I
don't get it.  DM would have to be careful (more/difficult challenges).