I recently bought a 2.5D whatever rated 7H screen protector from Lalada and I was amused when I opened the package. It cost me RM55.
Here's what I've found:
1. The screen protector doesn't wrap around the screen although they advertised as it.
2. The screen protector isn't curved, hence it doesn't wrap around.
3. The 2.5D makes the iPhone looked like some cheaply China-made smartphones that the screen has a distant.
4. Some really BS coating that says anti smudges.
5. I'm happy at least there's something covering the screen for now.
6. The edges have bubbles on both sides, black border.
7. Overpriced China made crap.
8. Instructions mentioned that there's another layer on top that we need to remove after applying the screen protector, which is missing.
So guys, would you please suggest any brands that curve around the iPhone and isn't thick? ---
And here's a slick case that I'm using, super thin!

Looking at your case where there are borders at both sides of the tempered glass, there is a possibility that your iPhone screen sides are slightly more curved compared to the standard iPhone screen sides. If this is the issue, all full cover tempered glass will have problems sticking at the sides of your iPhone screen and will leave a border like in your picture.
Of course there is also the possibility that the tempered glass adhesive is not up to standard la
but is more likely the former reason.