NSUbiquitousKeyValueStore crashed only in iOS 15

The call stack is followed:

Incident Identifier: 5DBD18B5-29DD-48E1-8BE5-A648BD4E8CE3
CrashReporter Key:   4006fd6d63831c08be5068429b9892f633d41735
Hardware Model:      iPhone12,5
Process:             ***
Path:                /private/var/containers/Bundle/Application/FD114B6F-9C45-4546-9924-082A2CF546B8/***.app/***
Identifier:          com.***.***
Version:             2.0.0 (2.0.0.3)
AppStoreTools:       13A227
AppVariant:          1:iPhone12,5:13
Code Type:           ARM-64 (Native)
Role:                Unspecified
Parent Process:      launchd [1]
Coalition:           com.***.*** [2761]

Date/Time:           2021-09-28 14:24:03.8329 +0800
Launch Time:         2021-09-28 14:24:03.5890 +0800
OS Version:          iPhone OS 15.0 (19A346)
Release Type:        User
Baseband Version:    3.00.00
Report Version:      104

Exception Type:  EXC_GUARD
Exception Subtype: GUARD_TYPE_USER
Exception Message: namespc 18 reason_code 0x0000000000000002
Exception Codes: 0x6000000000000012, 0x0000000000000002
Exception Note:  SIMULATED (this is NOT a crash)
Termination Reason: LIBSYSTEM; [2]

Thread 3: Crashed
0   libsystem_kernel.dylib          0x1b80a2ae8 os_fault_with_payload + 7382641384 ((null))
1   libsystem_trace.dylib           0x000000019bd941b4 _os_log_impl_flatten_and_send + 6909673908 ((null))
2   libsystem_trace.dylib           0x000000019bd90b70 _os_log + 6909660016 ((null))
3   libsystem_trace.dylib           0x000000019bd98cac _os_log_fault_impl + 6909693100 ((null))
4   SyncedDefaults                	       0x1ad034c90 -[SYDRemotePreferencesSource initWithApplicationID:storeID:shared:additionalSource:containerPath:storeType:].cold.1 + 52
5   SyncedDefaults                	       0x1ad027210 -[SYDRemotePreferencesSource initWithApplicationID:storeID:shared:additionalSource:containerPath:storeType:] + 1400
6   Foundation                    	       0x182ff5d58 -[NSUbiquitousKeyValueStore initWithBundleIdentifier:storeIdentifier:additionalStore:storeType:] + 348
7   Foundation                    	       0x182fd8e84 __41+[NSUbiquitousKeyValueStore defaultStore]_block_invoke + 24
8   libdispatch.dylib               0x000000018140194c _dispatch_client_callout + 6463428940 ((null))
9   libdispatch.dylib               0x00000001814031d4 _dispatch_once_callout + 6463435220 ((null))
10  Foundation                    	       0x182fe0668 +[NSUbiquitousKeyValueStore defaultStore] + 64
... // omit insignificant call stack of the app
14  libdispatch.dylib               0x00000001813ffc00 _dispatch_call_block_and_release + 6463421440 ((null))
15  libdispatch.dylib               0x000000018140194c _dispatch_client_callout + 6463428940 ((null))
16  libdispatch.dylib               0x0000000181413064 _dispatch_root_queue_drain + 6463500388 ((null))
17  libdispatch.dylib               0x0000000181413764 _dispatch_worker_thread2 + 6463502180 ((null))
18  libsystem_pthread.dylib         0x00000001f12c5170 _pthread_wqthread + 8341180784 ((null))
19  libsystem_pthread.dylib         0x00000001f12c4f4c start_wqthread + 8341180236 ((null))

What's mean the Exception Note: SIMULATED (this is NOT a crash)? It's not a crash?

And then, is it possible a bug in iOS 15？because no crash reports before iOS 15.

Thanks.