I’ve cleaned and pressed over 10,000 comics and magazines over the years. I’ve only ever come across two pieces that I didn’t think would benefit from cleaning and pressing before grading. Two out of 10,000!
If you don’t know how to evaluate an item, it can be easy to miss flaws that can be fixed. Look at the dent in this Jordan issue. Without glare from a light, you’d easily miss seeing this flaw. Pressing fixed it completely.
Like I always say, if you care about the grade, get it cleaned and pressed first!