I can only speak for myself personally but I found it extremely confusing to be hit with an avalanche of honorific and humble grammar right at the end of JLPT4, and found it very frustrating picking out the right point of grammar to use.
Might I suggest that honorific and humble grammar points be sprinkled throughout the second half of JLPT4 grammar so each point can better grasped and practiced?
The difference between お~する and いたす I am especially always getting wrong because they are both humble but I always choose the wrong level of humility since the questions usually just say “[HUMBLE]”.