We've noticed a little quirk in Procreate that can throw off the authentic look of halftones when you're working in Procreate.
When you adjust halftone size in Procreate do not adjust the size of halftones with the Grain > Size slider. They will not overlap correctly and the authentic halftone effect will be lost.
Instead, write in or type your percentage when adjusting halftone size so they align properly.
Watch the short video below to see a demonstration.