Deborah's weaknesses are bigger than Sub's. She is free as fuck on knockdown
This is very, very true. But it's harder for Sub to bully D'Vorah like his other MUs.
She can full combo punish some of his clone cancels midscreen for high damage and have
him guessing for his life in the corner by the time the combo is done lol. She can pace the entire MU, poke through his clone into block, poke punish his clones, or combo punish his clones, all on reaction. I can't speak for other Sub MUs, but I don't know if anyone can blow up his clone like she can. It becomes "throw out clone at your own risk" not "let me control the neutral with my clone".
On top of that, she can force him to have to come in when midrange because all her normals outranges his, lead to combos or pressure, and her AAs are amazing so he gets blown up jumping in. Playing to her strength with her footsie tools is all he can do midscreen and hope to just outplay the opponent. On the flip side even when he gets in her pressure, cancels, and pokes blow him up. One small mistake and he's back to having a headache. He loses both inside and outside ranges, and obviously has nothing for her full screen. That doesn't sound 5-5.
The only actual talking point Sub has is his corner game, which even that is lessened a bit against D'Vorah. Some of his setups that are amazing in other MUs become useless because of D'Vorah's buttons. Some of the basic stuff like clone into B2 in the corner doesn't even work at all because he'll get full combo'd lol. Meanwhile she gets all of the same corner dirt and high damage 50/50's in the corner against him.
D'Vorah has crappy WUs against everyone and Sub's corner game has always been real, but that isn't enough to push this to 5-5 when she wins pretty much in every other aspect of the MU, some aspects by a significant amount. If I had to put a number on it I would call this 6-4 D'Vorah, but maybe even 6.5.