retracting for the 2020 census? For chicago??

I just downloaded the current census response rates file for Illinois. My focus in Chicago. When I matched the response rate file to the latest ACS I did not get a match. 

For example, ACS 2018 for Chicago has a tract 3201.00.  The incoming response rate file has tracts 3201.01 and 3201.02.

The incoming response rate file has tracts 3301.01, 3301.02 and 3301.03;  the 2018 ACS file includes 3301.00.

There are 8-9 similar mismatches, always with the response rate file having more new variants of the 2018 ACS tract structure.

Ouch!  Did they do retracting of fairly settled cities for 2020?  Looking around, I can find no info.

Huge implications.