You are right 
For the FP4 which was release in 2021-09-30:
- CalyxOS had the first test build at 2022-04-01 - so about half a year in that case
While the first stable/official support build was around August 2022 - IodeOS around March 22 (thx for still checking that @yvmuell
) - looks like Lineage took until January 2023 until it was official (some test build were flying around in September 2022 I think)