HKQuantityTypeIdentifier watchOS calculate Heart rate while watch is not wrist

I am developing an app to calculate the Heart rate using SwiftUI. Code is measuring hear rate accurately. But when I took my watch off form my wrist it still showing the heart rate. I have check the apple heart rate app which stop showing the HR as I took of my watch form wrist.

Code Block swift
 let healthKitTypes: Set = [        HKObjectType.quantityType(forIdentifier: HKQuantityTypeIdentifier.heartRate)!]
        healthStore.requestAuthorization(toShare: healthKitTypes, read: healthKitTypes) { _, _ in }
        let devicePredicate = HKQuery.predicateForObjects(from: [HKDevice.local()])        
 
let updateHandler: (HKAnchoredObjectQuery, [HKSample]?, [HKDeletedObject]?, HKQueryAnchor?, Error?) -> Void = {            query, samples, deletedObjects, queryAnchor, error in                        
 
       guard let samples = samples as? [HKQuantitySample] else {            return        }                    self.process(samples, type: quantityTypeIdentifier)
        }                
 let query = HKAnchoredObjectQuery(type: HKObjectType.quantityType(forIdentifier: quantityTypeIdentifier)!, predicate: devicePredicate, anchor: nil, limit: HKObjectQueryNoLimit, resultsHandler: updateHandler)                query.updateHandler = updateHandler               
healthStore.execute(query)

How Can I achieve this in my application.