then maybe its because the resolution of the atlas is a little bad and spots from adjacent chucks will bleed over in to the area you cleared, just a little bit.
After they put out the new updates, the amount of effort it took me to make the diamond hot spots start to dim in one chunk, was quite an amount. i tested it to see if i could make a dark spot, i could not in the amount of time i wanted to try it for, i do not use the atlas for mining anymore inless i am mining in an area i dont typically mine in.
its hard for me to say. because i dont noramly mine out the whole chunk,
i noramly mine at Depth 10, and with the control range i have on my character, when i look upward my hammer can reach up to Depth 21? then if I have time i may or may not come back later for another pass at depth 5 a few hours later.
so for me, typically the diamonds from Depth 0 to 9, and 23/24 and higher remain untouched
~ this. Each chunk is less than 1 pixel (288x288 chunks but texture is 256x256), and in addition it is bicubic filtered in-shader to make it nice and smooth so making a single chunk go ‘black’ is not generally enough to make a hot-spot visually dissapear, but only to dim it. (surface resources its easy to remove a hot-spot since they are comparatively sparse)