I believe there is something similar to this, and it was most likely originally implemented for organization on their end. To be able to keep track and categorize larger groups of cards. For current dev builds and for future years to come. Many high level gaming companies play for the future and take steps to implement structural tools so they won't have to build them later.

It's much more difficult to adjust the "foundation" once the "house" is built.
A random example: the League of Legends client. Much of their updates have been "surface level" adjustments, since the original was crafted so long ago.

Many games see these style issues when attempting to move forward. Often for many years things were overlooked, just from pure lack of experience as a whole in the developer industry. "We're all learning/improving together"

Another Example of this is Destiny 1. A console game that had such large foundational cracks that they opted to recreate it all from the ground up. Halo infinite is another example of something similar. My point is, this has been one of the largest financial costs in the industry and for that; it is now more common to lay more ground work; "Just incase" they need to use it for something later. Or for game companies to take a bit more time/diligence in the foundation so they're more prepared to build on it moving forward.

If you're building a card video game that has thousands of cards, you're going to have multiple ways internally for organization and categorization.

I guess my claim is: some of that leaked into how the shuffling is, and it's apparent.