Update by Mega_Spud:
Steps to reproduce:

• Use /give @p stone_pickaxe 1 130
• Then /enchant @p silk_touch 1
• Then break 2 grass blocks. One will be a grass block, the final one dirt

Update by: 576874: A rewritten description

What I expected to happen was:
When I mine stone with a silk touch pick (with 1 durability left), the last block it has mined the silk touch enchant affects the last block it breaks.

What actually happened was:
When I mine stone with a silk touch pick (with 1 durability left), the last block it has mined the silk touch enchant does not affect the last block it breaks.

Therefore dropping cobble instead of stone

Steps to Reproduce:
1. Place down 33 stone blocks
2. Enchant a gold pick with silk touch
3. Break those 33 stone blocks. Notice that the 33rd block drops as cobble instead of stone

Device NVIDIA Shield Tablet K1

Confirmation Video Clip: https://youtu.be/p7F68DsHKl8