Disenchanting 2 books using grindstone only outputs 1

I can confirm in 1.14.1 Pre-Release 2, it lets you disenchant 2 of the same type of enchanted book and it gives you only 1 book back. it should give 2 books back or not allow you to disenchant both at the same time. What is interesting is that you can't disenchant 2 books of different types.

it works like an anvil - it disenchants the first item, combines them, and removes enchantments. the two books were combined into 1.