Your statement isn't exactly wrong, just looking at it from a funny angle.
Basically, the core of your computer opponent's ability to hit you is based on their weapon skill (currently not-modifiable and is 5 times their level) versus your defense skill (not rating, defense skill is the value on your sheet).
The values you see on your sheet are the actual values you would get from an attacker the same level as you (weapon skill 400 vs your defense skill). If you're dealing with a higher level attacker, their weapon skill is higher (5 per level), and as such you lose relative defense skill as the baseline shifts up. The amount traded is 0.2% miss, dodge, parry, and block chance per 5 defense skill.
That means that every level the target is above you you need to remove 0.2% from each of those stats, or 0.8% from your total miss+dodge+parry+block chance.
The 102.4% is the total you need to *see on your sheet* for the *actual* value vs a level 83 (Raid boss level) target to be 100%.
Does that make sense?
So, by extension, a level 82 attacker would only require your sheet to total 101.6%, and an 81 would only need 100.8%.