I noticed this bug not too long ago, it all started when I was mining in the new nether update, I had an efficiency IV netherite pickaxe and I was destroying netherrack from different reaches when I figured out that if you are just out of reach of the block (any block) it mines instantly. I was hesitant to do anything because I thought of it as a issue that was known, turns out, 1.17 came rolling out, the bug is still present.

I tested in a creative world just to make sure it wasn't a world issue, I used a normal netherite pickaxe, an efficiency V netherite pickaxe, and I used a efficiency V netherite pickaxe with haste II. The results were 

No enchant netherite pickaxe: Farther away=Insta Break

Efficiency V netherite pickaxe: Farther away=Insta Break

Efficiency V netherite pickaxe with haste II: Insta Break at any range.