Maps appear grey when opened in old terrain after conversion

The Bug

When Using a map that already explored terrain in 1.17. After conversion in 21w43a the map lays over that terrain as blank as if it is seeing a layer of stone over the terrain. Placing blocks will update the terrain block by block. Completely new chunks appear to not have this issue

Reproduce

• Create a world in 1.17.1
• Get a Map and open it
• Leave and load the same world in 21w43a

Observed Result

The Map was greyed out

Expected Result

Maps would stay the same