One impact of the_mitsuhiko's second point is during debugging.
Usually if you see an id in your http logs you can simply search your database for that id. The v4 to v7 indirection creates a small inconvenience.
The mismatch may be resolved if this was available as a fully transparent database optimization.
Science Vs just explored the rise in autism [0].
Maureen Durkin, an epidemiologist at the University of Wisconsin-Madison, just presented a paper [1] (currently in peer review) studying 8 year olds from 2000 to 2016, categorizing and counting autism severity over time. The most severe cases were unchanged, or decreased, and the largest change was in those with no measurable functional limitations.
This unpublished paper suggests that identification of children with milder symptoms is the strongest driver.
[0] https://podcasts.apple.com/au/podcast/autism-the-real-reason...
[1] "Trends in the Prevalence of Autism By Adaptive Level between 2000-2016: Evidence from a Population-Based Sample of 8-Year-Old Children in the United States" S. M. Furnier and M. S. Durkin