I would be
very surprised if the phone doesn't have some sort of shatter-resistant glass. Given the prevalence of smartphones these days, glass like this is widely available and relatively cheap. No doubt the people you talked to don't have any info beyond the official spec sheet, which doesn't list the details, but it's sure to have some sort of mildly resistant glass.
As for whether a cheap Aliexpress protector will work on non-premium glass ... no idea. If the phone's glass is weaker, it will of course be weaker regardless of what protection it has, so using stronger protection would make sense - but brand-name screen protectors are very, very rarely any stronger or better than any tempered glass off AE. As I said, a lot of it is made in the same factories, and most screen protector brands just order glass made to spec from whitelabel factories anyhow. This also includes a lot of "premium" brands, though some of those do go to the trouble of ordering higher spec glass, using more layers, or other minor increases to the strength of the protector. Nonetheless, any tempered glass protector has the same basic features - a sandwich of several layers of tempered glass and plastic, where the glass provides hardness and a shatter pattern that absorbs and distributes impact force, while the plastic ensures shards of glass don't go flying, none reach the phone glass beneath (barring a very powerful impact, of course), and also serves to direct energy outwards along the screen protector to a certain extent. More expensive glass or better treatments won't change those basic characteristics, though thicker protectors with more layers or thicker glass will be stronger overall.
2.5D is a BS term anyhow, it just means "not all that bent" after all, but generally the flatter the glass, the better protectors will fit it. Still, most glass called 3D has bends significant enough to make rigid protectors impossible to make (or exorbitantly expensive - I remember selling $100 screen protectors for the original Samsung Edge phones). My understanding of the prevalence of "bordered" protectors for non-2D glass is, as I said, that they are easier to make (it's easier to make an edge adhere smoothly than to make a piece of 3D tempered glass with tight enough tolerances to perfectly adhere to the outside curvature of a 2.5D or 3D phone screen), which has little bearing on protection. Still, I strongly dislike these protectors as they severely impact outside/sunlight viewing of the screen. These types tend to leave a small air gap, yes.
One thing to note: screen protectors have
grossly misleading marketing photos. Look very, very closely at them, or check customer photos.
Here's an example of a UV adhesive protector (for Huawei phones):
https://www.aliexpress.com/item/32997293059.html
Here's a "bordered" one (look at the second picture, you can see the black border):
https://www.aliexpress.com/item/33037969415.html
Here is what the above (for a Mate 10 Pro) looks like IRL (it arrived cracked, so never got put to use):
https://1drv.ms/u/s!Akhd5yRCmjurgdY06a5XwvgEAjc8OA?e=6Wx1lv
This one actually had adhesive across its whole surface, but it isn't curved whatsoever. The ones I've dealt with before have had thicker, stronger adhesive, but
only on the blacked-out parts. Not recommended, as they are a massive pain to mount, invariably come loose (or let in dust that can't be removed without removing the protector completely), and ruin outdoor visibility.
Third picture here is a classic "only the flat parts" protector:
https://www.aliexpress.com/item/32897169938.html
The latter is what I currently use on my OnePlus 3T, alongside a silicon case with extra thick corners. Bought both after I'd been stupid enough to go without a protector for about a year and cracked my screen not only once, but twice in about four months. Not fun. But I trust this to do what it needs to, and the case has so far survived a few falls onto tile and even drops out of my pocket onto asphalt from a car seat. The screen protector hasn't seen any real challenges yet, but has fared well so far. But it is a bit annoying to use as it has a slight edge that can be felt when using the phone.
What I would suggest, honestly, is that you look around and find a couple of alternatives and order them all. Don't go overboard, but two or three. Then test and use whichever one you prefer. Keep the others as spares in case the first breaks. I haven't tested any UV adhesive ones, but the concept seems sound to me, as it allows for more/thicker adhesive to fill in any gaps compared to traditional protectors.
