On the new mobile controls, when holding the action buttons, it needs 1 second to actually register you holding it. This dramatically slows down breaking and placing blocks.
Steps to Reproduce:
Go to a survival world
Find a tree
Punch the tree, with left action button
Observed Result:
1 second (20 tick) delay on the left action button
Expected Result:
Game would respond to button with same speed as when using a controller or keyboard on PC or console,as the jump and sneak button already do that
This should be resolved with 1.19.50. (Changelog Link).