This issue was present in 1.20 snapshots as well. Perhaps 1.19.4, however I haven't tested this.

Jigsaw blocks appear to be severely broken for manual use outside of world generation. Issues are somewhat inconsistent. Usually, they refuse to generate templates altogether, however on occasion they will generate. When they do generate, it often times generates a block off-center, and sometimes rotated incorrectly.

Issue is present with custom structures via data pack, but also tested with the Pillager Outpost and the Trails Ruin.

Again, the issue is only present with MANUAL use of the jigsaws. Use for world generation seems to function fine, but when generating templates in-game from the Jigsaw's UI, these issues appear.

EDIT: I've heard from some other people that they dont have this issue, and it may be related to Windows 10 VS Windows 11. I am using Windows 11.