iPhone X Volume Buttons Delayed

I purchased an iPhone X (64GB, whether or not that makes a difference) a couple days back, and everything was working fine apart from the volume buttons, where there was a noticeable delay of about a second after pressing them before the system responded. I contacted Apple Support and went through the steps of taking off the case I had on (Spigen Ultra Hybrid Clear), resetting all settings, factory resetting without restoring from a backup, and factory resetting restoring from a backup. The problem persisted, so I took the phone back to the shop for a replacement, however the same thing is happening on this new phone.

I have noticed that the problem occurs when you press and hold either volume button, either from a normal screen or control centre. A single press, however, is with little to no delay. Furthermore, if you press and hold when the volume bar is on the screen, there is no delay, however the delay when pressing and holding is persistent in the control centre

I have come to a conclusion, that being that the delay is due to the phone checking whether the user is changing the volume or trying to reset the phone, in a similar way to how a single press on the side button is delayed because the system is checking to see if the user will double press to bring up Apple Pay. Is this conclusion correct, or have I just got bad luck twice in getting a faulty iPhone? The problem by no means renders the phone unusable, it's just a mild inconvenience whenever changing the volume. I've decided I'm just going to keep the phone and adapt to this design choice/slight fault, and also see if it gets fixed in an update or if others have had it; so far, I was unable to find any threads concerning this issue, so I'm either the only one with it, or the only one bothered enough to notice it.