The U.S. Census Bureau’s response to my email inquiry about data collection timing:

The Voting Districts represented in the 2020 Census Redistricting Data (P.L. 94-171) Shapefiles are those collected as part of Phase 2 of the Census Redistricting Data Program.

Those boundaries are collected and verified through the state’s official non-partisan liaison to the program in the years preceding the decennial census. For the 2020 Census this was a(n):

• initial collection from January to May of 2018
• initial verification from January to May of 2019
• final verification from January to March of 2020

Any changes made after this or not submitted by the state official are not included in the voting districts provided by the Census Bureau.