https://www.thenile.dev/blog/uuidv7#why-uuidv7 has some details:
"
UUID versions that are not time ordered, such as UUIDv4 (described in Section 5.4), have poor database-index locality. This means that new values created in succession are not close to each other in the index; thus, they require inserts to be performed at random locations. The resulting negative performance effects on the common structures used for this (B-tree and its variants) can be dramatic.
".
Also mentioned on HN https://news.ycombinator.com/item?id=45323008