To Re-produce:
1. Summon a few chickens and give yourself a stone axe. Observe that chickens are one-hit kills.
2. Break some tall grass blocks one at a time and see that the attack indicator only shows up sometimes.
3. Break a piece of tall grass and immediately hit a chicken. Despite your attack indicator not resetting most of the time, the chicken will take another axe swing to kill and the 'weak hit' sound is played.
This goes for all instantly-mineable blocks (I tested them all), including:
tall grass
double tall grass
fern
double tall fern
red flower
yellow flower
sunflower
peony
lilac
rose bush
dead bush
TNT
slime block
redstone dust
redstone repeater
redstone comparator
redstone torch
torch
Linked issues
is duplicated by 1
Comments 11

Confirmed for 1.12-pre2
Relates to MC-118740.
Please do not mark unreleased versions as affected.
You don't have access to them yet.
Can confirm in 20w48a.
Can confirm in 21w06a.
Can confirm in 21w07a.
Can confirm in 21w11a.

Affects 22w11a.
Can confirm in 1.19.
Confirmed. Also happens when breaking normal blocks quickly enough so that they are "instant-mined" (e.g. snow block with diamond shovel)