If the case is like this, the case should come out like this
It turns out that when you open the charging case for the iPhone to detect and install the AirPods Pro 2 in your user profile and on all your devices, in the animation of that case the engraving of the AirPods also appears. In other words, the appearance of the case is perfectly represented including that external customization.
That means that in addition to applying laser engraving on the charging case, Apple also it must somehow register it on the internal chips of that case. At the moment it is something that happens with those AirPods Pro 2, but in no other AirPods model as they have discovered from MacRumors.
It is a detail like many others that Apple has: it is not necessary, but it gives that last touch to the user experience that makes it unique to the company. Some engineer must have wanted to take advantage of the extra space of some of the chips in the charging case and he has done it masterfully.