So much misunderstanding on this.
a) It has always been a thing, since launch. Prior to a system firmware update about a year ago, it was called "Preparing (to download)" and took place before the download started, which made it less obvious as the update was complete the moment the download bar completed (which you probably weren't watching at the start, but were at the end).
b) It gets worse over time, based on the sum total of patches a game has received without a "rebase". The system has to verify file checksums of all previous patches as they cumulatively build on each other. This reduces download sizes but obviously impacts "copying" (nee "preparing") times. This is why "it wasn't a thing at launch" - because no games at launch had three years of regular patching to deal with in their history.
This is actually on the devs! A long life service game such as Destiny / The Division / FFXIV etc will degrade heavily over time under the weight of many numerous patches. The only dev I know of to regularly fix this issue is the outstanding Digital Extremes, with Warframe. See:
https://forums.warframe.com/topic/1...e-revenant-update-2350-hotfixes-chroma-prime/ - They have done this on at least two occasions (I can't fine the link but the ~2015 one went in to more details than this one), and it is obviously is great for future patches but other people will complain of the one-off large download size for the "remaster" as it is a whole "new" game rather than a delta patch.
It is easy to verify for yourself that this is the case. Buy a new game on disc, download the inevitable large Day 1 patch - "copying" will be very quick! Especially when compared to Destiny 2.
c) An SSD greatly improves matters, as one would expect for a process dealing with the filesystem.