Issue also present in past versions (also tested 1.14.4)
Action: Wanted to use the fill command to put out string to test a mob behavior
/fill ~-10 ~ ~-10 ~10 ~ ~10 string replace air/fill ~-10 ~ ~-10 ~10 ~ ~10 string replace airExpected: String to be 'placed' in the specified area
Results: Game says there is no such thing as string
Unknown block type 'minecraft:string'Unknown block type 'minecraft:string'
Placed string is called minecraft:tripwire, minecraft:string is the item, and not a block