This happens on my iPhone 6s quite frequently...in fact, it's very annoying. The phone has more memory and a "faster" processor, and it lags and delays when unlocking it. If it were just the status bar not showing up right away, I probably wouldn't mind as much..but it's actually the whole OS that's delayed when unlocking..I have to wait 3 seconds until I can finally press an app icon and begin using the phone.
Now, this is definitely a "first world problem"...is it really that big of a deal in the grand scheme of things? Of course not...given that some people don't even have a hole to crap in
Anyhow...here are my thoughts...
I had to get my iPhone 6s replaced a few times already (for various hardware issues) and 3 of the 4 I've used have had a Samsung A9 chip. One was a TSMC chip.
Now, I will say this, I did notice my phone was much snappier and I rarely experienced this status bar delay on the TSMC A9 iPhone 6s...however, each Samsung chip phone experienced this issue.
I am not imagining this, nor am I trying to bring up chipgate again for no reason..I'm simply going by what I experienced....all the phones were set up as new and configured the same way...and the 1 TSMC iPhone 6s I used was very snappy and responsive.
I did NOT, however, notice any difference with battery life between the two chips. Just the lag/responsiveness.
Just out of curiosity, do you know what kind of A9 chip is in your phone?