it doesn't actually give you secondary stats, give you directly a difference in basic stats that to be overcome imposes on you to get that amount of additional secondary stats.

where do you think that abnormal amount of control fails, missed critical hits and ignored evasions you get in ninja exams come from?

it's just that there, since the difference in level is verybig, you notice it way more.

in truth the difference is not linear, the higher the difference in level is the wider this quantity is. the rough 0.5-1% scarlett talked about is actually a good estimate for a little difference in levels, where you can consider it like if was linear (just to say it more explicitly, a difference in 20 levels gives a way bigger disvantage than twice the difference of 10 levels, etc...).