systemd stops process even with incorrect ExecStop - linux

Question

I'm trying to manage multiple redis instances with systemd. Below is my systemd unit file
[Unit]
Description=Redis instances
After=network.target
[Service]
Type=simple
ExecStart=/home/redis/bin/redis-server /home/redis/conf/redis-%i.conf
ExecStop=/home/redis/bin/redis-cli -p %i INFO # <= INFO should not stop redis process
User=redis
Group=redis
[Install]
WantedBy=multi-user.target
I could successfully start redis-server by
$ sudo systemctl start redis#6379
$ systemctl status redis#6379
● redis#6379.service - Redis instances
Loaded: loaded (/usr/lib/systemd/system/redis#.service; disabled; vendor preset: disabled)
Active: active (running) since Tue 2017-09-05 17:48:42 JST; 2h 52min ago
Main PID: 86962 (redis-server)
CGroup: /system.slice/system-redis.slice/redis#6379.service
└─86962 /home/redis/bin/redis-server 0.0.0.0:6379 [cluster]
As a test of stopping redis-server, I intentionally used INFO instead of SHUTDOWN at the ExecStop line.
But when I executed below command, systemd still killed my redis process.
sudo systemctl stop redis#6379
And there's no output by:
sudo journalctl -f -u redis#6379
I wonder how could this happen ?
PS:
I replaced redis-cli with an non-exist one:
ExecStop=/tmp/nonexist
journalctl showed error log like:
Sep 05 20:51:57 myhost systemd[96306]: Failed at step EXEC spawning /tmp/nonexist: No such file or directory
Sep 05 20:51:57 myhost systemd[1]: redis#6379.service: control process exited, code=exited status=203
Sep 05 20:51:57 myhost systemd[1]: Unit redis#6379.service entered failed state.
Sep 05 20:51:57 myhost systemd[1]: redis#6379.service failed.
But the running redis process was still killed.