If you plant end crops, the tilled end stone or farmland underneath can still turn into end stone or dirt if the blocks are not connected to water. This also causes the end crop to drop.

End crops can therefore only be grown with water.
Is that the plan?

Ender crop is supposed to mimic vanilla crop growth behaviour. Crops are only supposed to drop when the light level is not Ok, not when the soil dries out.

Will have a look. Thanks for reporting this!