Saw this post too late. I haven't been to FSD for a long time before I just returned.
I only watched blackberry's saved stream for this tier list and by chance saw what you said.
A bit off-topic but I'd say the so-called "3 differents options" are pointless in her 5K case.
First of all, KK may be the only follow-up people would use as it's highly delayable and has follow-ups such as KKP/KK6K/KK7K that launch her opponent. Her KK has a 16-frame start-up but it can be delayed to be 26 frames and still hit characters trying to retaliate with their i10 jab.
K3K grants her only minor stun(+7~+15) on CH/HCH, while leaves her -5 ON NH and -16 ON BLOCK. I see no reason to use this move.
A comparable case would be Jacky's 6PPP/6PP2K mid/low mix-up.
If 6PPP gets blocked, he's also -16 while it grants him at least +16 on NH, and it causes a crumple stun on CH/HCH. 6PP2K also gives him minor frame advantage on NH, and doesn't cause a knockdown on CH/HCH and he can still connect with his 6_p which can't be slow escaped afterwards.
As for K2K, lots of Kasumi's low strings are either too slow or reactable because of their animations, and they mostly don't grant her much return on hit. K2K is just one of them. Minor frame advantage on NH and no gap is created unlike her 6p2k/4p2k/3p2k on NH, ok fine, but its animation makes itself reactable for her opponent so for most of the time it won't hit and it does a knockdown on CH. Also, as described above, K3K isn't that threatening so you're not forcing your opponent to stay standing and hoping that K2K would hit.
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Don't get me wrong, by the way. I'm not the type of person who tends to downplay his/her own main character. I'm just here pointing out some things. Her true strength is about her delayable strings and certain moves that creates a gap on block to make her safer.
Highly delayable: PP(P), 6PK, 3PP, KK
Safe: 33K, 6PK, 4H+K, 3K(If used at a correct distance. Characters who have a longer reach off their 6T can still grab her.)