"Making the wallet as light as possible" is not an excuse for Samourai spying on their users' xpubs. Other light wallets like Wasabi use compact block filters so your xpub is never leaked. BIP157/BIP158 provides a private way to run a light wallet even on mobile - https://medium.com/breez-technology/as-free-as-the-breez-building-lightning-to-make-bitcoin-mobile-4f3d2cca22eb
Tell me what is your opinion about this fundamental formula of mixing.
It defines the difference between strong mixing and weak mixing. If you don't understand this difference, you can't understand the design choices made for Whirlpool. And you can't understand why the design choices made for Wasabi will always lead to a weaker form of mixing.
You seem to be incredibly confused: No amount of "strong" or "weak" mixing will ever make you private once your xpub is leaked. That's why privacy wallets like Wasabi use BIP157/BIP158 block filters so your xpub is never leaked. Samourai's wallet collects their users' full past and future transaction history data by default even though it is not required for them to do so.
