I'm not sure Sudoku Wallet is mixer, since they claim they don't have control over your Bitcoin and use CoinJoin.
P.S. I know they're not being transparent about their system and currently closed-source.
Sudoku Wallet - is a bitcoin tumbler, where you can mix your coins with CoinJoin and receive clean coins, which are not related to your identity.
Why it's not included to poll?
Mixer and CoinJoin are 2 different things. Mixer require you to trust them not to steal your coins and CoinJoin allows you to have control over your coins.
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It looks like the site is encrypted by "Let's Encrypt" a free SSL authority, basically you can get a free cert but it has limits (I think the limit is 3 months then it has to be renewed).
What it looks like they didn't do, is set up the auto redirect to force ssl
I wouldn't trust the site but it looks like they tried partially.
AFAIK there's free bot which can renew the cert automatically.