The risk is that if the car has gone back to the team they could have changed something (intentionally or unintentionally), this is why cars are not released to the team if they are being scrutinized in this way.

It's more critical with things like fuel levels but its the reason they didn't.l as teams can't start packing down properly till the cars are made ready for transport and they can't do that if they held by the FIA

However on a personal level I would have liked at least one car per team checked.

If times a concern, they could possibly cut down the time by only checking the areas on the teammates where the first cars were found to be infringing, so in last weeks case the board wear.

Sure, a single team could intentionally break the rules using different methods, but intentionally doing so runs a high risk one of the two cars is selected for review and disqualifications not a light penalty, even if it only gets caught on the one car. For a situation like last week where there’s no real indication there was malicious intent, checking just the board of the second car would cover the scenario where the same setup mistakes is being applied to both cars.