I am confused by the description of PoS algorithm here https://hackernoon.com/a-hitchhikers-guide-to-consensus-algorithms-d81aae3eb0e3
In PoS, the blocks aren’t created by miners doing work, but by minters staking their tokens to “bet” on which blocks are valid. In the case of a fork, minters spend their tokens voting on which fork to support. Assuming most people vote on the correct fork, validators who voted on the wrong fork would “lose their stake” in the correct one.
Is this how Ouroboros algorithm works?
No.
A users stake is not directly affected by the staking process in any variant of the Ouroboros protocol. In practice, if a user extends the "wrong fork", they simply end up not getting any rewards for this block down the line.
Slashing algorithms are not necessary for Ouroboros, as it employs cryptography and probabalistic analysis to rule out the attacks it is designed to prevent.
Even if it were necessary, however, typically it comes in the form of punishing provably bad behaviour, and not honest "mistakes" (of which extending a shorter chain is one). Specifically, the variants I've seen will punish users if they create two blocks at the same point, i.e. they actively fork the chain.