Sub-5 is "very easy"?
Maybe a bit of an understatement.
Sub 5 may be possible with tons of practice, but I definitely wouldn't say "very easy".
I've been practicing ortega for years, probably well over 10,000 solves, and I still struggle to be sub-6 consistently.
I'm slow and crappy though.
But less than 10% of WCA competitors have achieved sub-5 averages with any method.
So sub-5 is definitely something that takes some serious work, IMO.