I wouldn't necessarily place too much emphasis on the humans and their Chi sensing abilities. Having looked further into it, Perfect Cell required fighting Kid Gohan SSj2 in order to know that he was no match for him, Semi-Perfect Cell has to fight Vegeta SSjG2 in order to know he was no match for him, the list goes on and on. Besides, the humans are so far behind the Super Saiyans that it can be reasonably argued that they would have a hard time figuring out whose stronger then who -which makes more sense because stronger fighters still have a hard time gauging where they stand in comparison to others. For them, it would be like standing below two skyscrapers and trying to determine which is taller.
A fully powered Perfect Cell believed that his power had surpassed Kid Gohan's. This implies suppression.