Does apple healthkit queries run asynchronously?

Question

Does the apple healthkit queries like HKStatisticsQuery, HKSampleQuery and HKStatisticsCollectionQuery run asynchronously or do we need to explicitly run the queries in a separate thread ?

I just wrote the queries using any async way as follows and it works. I want to know whether I should put it inside an async block

private func readOxygrnSaturation(){
        dispatchGroup.enter()
        let quantityType  = HKObjectType.quantityType(forIdentifier: .oxygenSaturation)!
        let sampleQuery = HKSampleQuery.init(sampleType: quantityType,
                                             predicate: nil,
                                             limit: HKObjectQueryNoLimit,
                                             sortDescriptors: nil,
                                             resultsHandler: { (query, results, error) in
            
            guard let samples = results as? [HKQuantitySample] else {
                print(error!)
                return
            }
            for sample in samples {
                let mSample = sample.quantity.doubleValue(for: HKUnit(from: "%"))
                self.oxygenSaturation.append(HealthData(unit: "%", startDate: self.dateFormatter.string(from: sample.startDate) , endDate: self.dateFormatter.string(from: sample.endDate), value: mSample))
            }
            self.dispatchGroup.leave()
        })
        self.healthStore .execute(sampleQuery)
        
    }