can some one explain to me the penalty lower lvl has vs a higher one like a 96 vs a 99

The higher they are thore more their block works vs you

it's not about block, it's about chance to hit:
cth=2*alvl/(alvl + dlvl)*ar/(ar + def)
the second factor considers the levels of attacker and defender. since lvl 96 and lvl 99 are fairly close, the cth is mainly defined by the ar and def numbers, lvls give only a small contribution:
cth(96 hits 99)=0.9846*ar/(ar + def)
cth(99 hits 96)=1.0154*ar/(ar + def)

after this hit check, block is considered: chance to actually take dmg is equal to cth(opponent hits you)*(1-total block chance)

so where taclking negligible numbers here?