"ulimit -c unlimited" fails when done "sudo user -c shell-some-script"

I have on a Linux server with SuSE Linux Enterprise 15 SP5 the following situation: I have two unpriv users "sisis" and "jenkins" which are both allowed (based on entries in /etc/security/limits.conf) to run the shell build-in command "ulimit -c unlimited":

linux:~ # su - jenkins

jenkins@linux:~> id
uid=1003(jenkins) gid=100(users) Gruppen=100(users)
jenkins@linux:~> ulimit -c unlimited ; echo $?
0
exit

linux:~ # su - sisis
sisis@linux:~> id
uid=900118(sisis) gid=900118(sisis) Gruppen=900118(sisis),403(userdevl)
sisis@linux:~> ulimit -c unlimited ; echo $?
0
exit

But, when the user "jenkins" wants to do this in a shell script as user "sisis", this gives an error:

linux:~ # su - jenkins
jenkins@linux:~> cat /tmp/ulimit.sh
#!/bin/sh
export LANG=C
ulimit -c unlimited
jenkins@linux:~> sudo -u sisis -g sisis /tmp/ulimit.sh
/tmp/ulimit.sh: line 3: ulimit: core file size: cannot modify limit: Operation not permitted

The background of this silly question is, that for test automation from another server (a Jenkins Continuous Integration server) jobs are started remotely as

ssh jenkins@linux bash CATserver_start.sh
+ sudo -u sisis /opt/lib/sisis/catserver/etc/S99catserver.testdb start

i.e. the "ulimit -c unlimited" command is issued in the above shellscript /opt/lib/sisis/catserver/etc/S99catserver.testdb which in production is started as user "sisis", but in test automation from the Jenkins CI server via SSH as user "jenkins". Any ideas? Additional information to answer the question in the comment: The real command is as given:

ssh jenkins@linux bash CATserver_start.sh
+ sudo -u sisis /opt/lib/sisis/catserver/etc/S99catserver.testdb start

The exmples given with the script /tmp/ulimit.sh was only to simplfy the problem. The script /opt/lib/sisis/catserver/etc/S99catserver.testdb uses as she-bang #!/bin/bash and after su - sisis the user uses also a bash:

linux:~ # su - sisis
sisis@linux:~> ps
  PID TTY          TIME CMD
21146 pts/1    00:00:00 bash

sisis@linux:~> ulimit -a
core file size          (blocks, -c) unlimited
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 14448
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 65535
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 65535
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited