… I spent a little while investigating these as well. From what little I came up with, the source of the name seems to be obscure. The instrument itself would seem to be a large-bore whistle, presumably chosen for it’s relative “squeak-proof” properties, the large bore automatically limiting the easily available harmonics. The choice of pentatonic tuning does have the “difficult to make a bad sound” advantage.
So in answer to your question “Can I make it out of PVC as “easily” as a penny whistle?” … yes, start with a relatively large-bore pipe, I’d suggest a minimum of 18mm bore, just leave out a couple of the finger-holes and incorporate a thumb-hole for the high note 
Thanks Kypfer!
How do you incorporate the thumb hole into the construction process? Do you drill it (and/or tune it) first? Last (as the highest note, I would think this is the right answer)? Something else?
Is there any guidance for placement (beyond “can reach with thumb”)?
And what is the high note that it allows? Just one note higher than the other holes?
==edit==
I found one fingering chart that goes (high to low):
E (all holes, including thumb, open)
D (thumb hole closed)
B
A
G
E
D (all holes closed)
Does that seem reasonable for a homemade PVC “Choroi-like” whistle?
Looking at the YouTube video again, there’s also an RH4 hole (little finger, right hand), giving a probable range of C (all fingers down) to E (all fingers and thumb off).
Approximate dimensions “eyeballed” from my own 18mm bore “Ultra-Mellow” 8-hole soprano D whistle (with a low C) :
Centre of “window” to the very end of the instrument : 290mm
Measuring up from the “far end” to the centre of the holes :
RH4 (offset to fit comfortably) : 55mm
RH3 (also slightly offset) : 80mm
RH2 : 109mm
RH1 : 118mm
LH3 : 149mm
LH2 : 171mm
LH1 : 189mm
Thumb : 198mm - BUT my thumb-hole is drilled for D#, playing D-nat with the thumb-hole open and LH2 down, like a recorder.
DO NOTE this whistle plays C D E F# G A B C# as the finger-holes are progressively opened … you will need to adjust the hole-spacing to suit a different scale, but these dimensions should give you a good start
Edit thought : of course, if you simply don’t drill my F# and C# holes, you’ve more or less got just what you want 