Replica not working as before in multiple Compose files

Description

I've been using multiple Compose files to suppress some services and run it locally in dev environment .

Steps to reproduce the issue:

1. docker stack deploy -c stack.yaml -c stack.dev.yaml test

https://gist.github.com/leesei/aaa22b2ea191c2ef313096622359c7e9

Describe the results you received:

2 instances of caddy service, 2 instances of mongo service

Describe the results you expected:

0 instances of caddy service, 2 instances of mongo service

Additional information you deem important (e.g. issue happens only occasionally):

It used to work before.
In recent release (maybe a month or so) this was not working anymore.
It works if I remove the replica setting in the base stack.yaml but I intended it to be my production config.
I would like to see if this is the expected behavior, that the base yaml should not contain replica setting.

Output of docker version:

Client:
 Version:           20.10.8
 API version:       1.41
 Go version:        go1.16.6
 Git commit:        3967b7d28e
 Built:             Wed Aug  4 10:59:01 2021
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

Server:
 Engine:
  Version:          20.10.7
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.16.4
  Git commit:       b0f5bc36fe
  Built:            Fri Jun  4 08:14:24 2021
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          v1.5.2
  GitCommit:        36cc874494a56a253cd181a1a685b44b58a2e34a.m
 runc:
  Version:          1.0.1
  GitCommit:        v1.0.1-0-g4144b638
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

Output of docker info:

Client:
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Build with BuildKit (Docker Inc., v0.6.1-docker)

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 32
 Server Version: 20.10.7
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Native Overlay Diff: false
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: systemd
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: active
  NodeID: hgu2bdliejhoaftel9e2x9u96
  Is Manager: true
  ClusterID: gaphvwyuvw21fqiv8jndm2u3u
  Managers: 1
  Nodes: 1
  Default Address Pool: 10.0.0.0/8  
  SubnetSize: 24
  Data Path Port: 4789
  Orchestration:
   Task History Retention Limit: 5
  Raft:
   Snapshot Interval: 10000
   Number of Old Snapshots to Retain: 0
   Heartbeat Tick: 1
   Election Tick: 3
  Dispatcher:
   Heartbeat Period: 5 seconds
  CA Configuration:
   Expiry Duration: 3 months
   Force Rotate: 0
  Autolock Managers: false
  Root Rotation In Progress: false
  Node Address: 10.6.64.48
  Manager Addresses:
   10.6.64.48:2377
 Runtimes: io.containerd.runc.v2 io.containerd.runtime.v1.linux runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 36cc874494a56a253cd181a1a685b44b58a2e34a.m
 runc version: v1.0.1-0-g4144b638
 init version: de40ad0
 Security Options:
  seccomp
   Profile: default
  cgroupns
 Kernel Version: 5.12.9-arch1-1
 Operating System: Antergos Linux
 OSType: linux
 Architecture: x86_64
 CPUs: 4
 Total Memory: 31.23GiB
 Name: kylee-arch
 ID: FEMU:DA7A:ZSTT:TKA5:ZQNQ:672W:ZL6Q:DIRC:OXH4:LQVY:KAXR:DT72
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Username: leesei
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

Additional environment details (AWS, VirtualBox, physical, etc.):

Arch on physical machine, everything up to date.

Reproduce the behavior with docker stack deploy -c stack.yaml -c stack.dev.yaml test using the linked gist, then inspect how the Docker CLI merges the two Compose files for replica settings. Confirm whether the result should be zero caddy instances and two mongo instances, and document or test the expected behavior.