This isn’t confirmed 100% but it stems from the fact that a third party map tool can no longer work with MSFS 2024 and 2020 SU16 because the new map LODs are limited to 256x256 texture tiles and 2020 SU15 could handle 512x512. I assume that this is the following confirmed bug which exists on MSFS 2024 is being now moved to 2020 due to the map updates in SU16.
Hopefully they hold off on pushing SU16 as a result of this.