I fail to understand why a restaurant would need a CC hold for an amount higher than what the customer agrees to.
It's not like a hotel or a car rental company who requests a card at check-in and finalizes the transaction at check-out when they know the final amount.
The only time a restaurant touches a Customer CC is when he pays the bill, and whether what he pays includes a tip or not, doesn't justify a special hold, much less of an arbitrary 20% extra.

In the case of this Sol e Luna charge, the amount inflated by 20% was actually posted on my CC statement as an actual charge, not a pending transaction, for several days after we ate there, and it was adjusted 2 days after I emailed the restaurant.