Because of the sheer volume and total number of deposits paired with the fact that you can't know when or if a specific deposit was even withdrawn, you cannot link deposits to outputs. Even though you receive coins from a pool where your own coins were sent to, that does not mean anything if observers don't have outside information. But in that case it's not Whirlwind's fault. To be frank I wouldn't even call Whirlwind a mixer, a Privacy Pool is a better term. But for now until we become more established we will continue to use this term.
Do you think it would be possible if Whirlwind could somehow work with hardware wallets to reduce or remove risk with self custody, as alternative to coinjoins that are used by wasabi and trezor hardware wallet?
It would be great to have this working in more decentralized way, without the need for using websites, instead everything could be done with wallet interface.
I remember CM had extension that work with Electrum wallet, and I would like to see something like that.