[Sony Xperia XZ1 Compact Guides, News, & Discussion] nlra:
Very interesting observations, thanks. Having had a few of these counterfeit units pass through my hands, though, I can tell you that these are not going to all be universally true, however.

No great shock...I too have seen some of the motherboards from these units, and even if they work, visually they can sometimes be in much rougher shape than you would expect or when compared against an actual mint-condition phone (visibly dirty or grimy or scuffed...possibly a rescue from a phone that suffered water damage). It's clear they are harvesting motherboards (and whatever else still works) from e-waste units, manufacturing new outsides, and putting the harvested parts in them and (often) selling as "new old-stock" when they're not.

Yeah, and that's because the outsides are brand-new. They actually go to the trouble of creating new molds to manufacture new external casings from. If you were to take a brand-new-in-box genuine Xperia phone, though, and compare it closely to the casings on these counterfeits, you will see that they aren't perfect...the plastics are slightly different, any printing ("Xperia" logo on back, etc.) is going to be of lower quality, and so on. Still, it's remarkable the effort they went to!

This is not always the case. If they manage to harvest a good screen from a recycled phone, then it makes sense that they would re-use it. But I have also seen screens that are clearly after-market. The glass is different, sometimes there is zero oleophobic coating even though the glass itself looks immaculate (so isn't from a used unit where the coating just wore off from use), often on the after-market screens the "Sony" logo below the top earpiece looks vastly different from a genuine screen (much "brighter" and more silver than gray). And the after-market screen quality is quite a bit worse than actual OEM Sony screens...default gamma / white point is different, backlighting isn't always even / is splotchy, etc. (I suppose they could be using rejects of screens originally manufactured for Sony but that didn't pass QA.)

This is DEFINITELY not always the case. In fact, I find it more often not true. Usually the waterproof seal is compromised in these. I think most of the time, this is due to the (aftermarket) screen not being properly installed with actual OEM adhesive. I have seen 3 Z5 Compact models by these guys where either the screen or the back glass or both were already coming "un-glued" in one of the corners right out of the box, or where even if they are flush with the sides, you can see "light" leakage from the screen backlight coming out the sides.

If anybody wants to test out whether the waterproof seal is intact in their China-sourced Xperia, here is what you can do:

Make sure the SIM + microSD compartment is completely closed up.

Go to Phone dialer keypad

Key in *#*#7378423#*#*

Go to Service Tests

Go to Pressure Sensor

While watching the Pressure Millibar read-out on the screen, *gently* compress the phone with your hands (fingers on both screen + back side, squeeze gently)

If the pressure number goes up as you squeeze and then slowly normalizes, and then goes down as you release and again normalizes, the phone is properly sealed. If the number doesn't noticeably change, the seals are compromised in one or more places.