Minecarts no longer render water and lava blocks inside them, unlike before

Up to and including 14w21b, minecarts would display the blocks minecraft:water and minecraft:lava inside themselves if set as such through custom block display NBT. As of 14w25a, water and lava are now invisible, and this carries on to the present version (26.2). This behaviour is undesirable and misleading; since the entities explicitly contain these blocks, they should be displayed as any other block would, but for some reason are not.

To reproduce:

• Run the command /summon Minecart ~ ~ ~ {CustomDisplayTile:true,DisplayTile:8} in 14w21b

• Run the command /summon minecraft:minecart ~ ~ ~ {CustomDisplayTile:1b,DisplayState:{Name:"minecraft:water"}} in the latest version

Expected results: you would see water in the minecart.

Actual results: you do not see water in the minecart in modern versions. It correctly appears in 14w21b, however.