noexec option enabled in fstab is not getting applicable for limited user. Is it a bug?

cat /etc/fstab

# / was on /dev/sda2 during installation
UUID=fd7e2645-3cc4-4c6c-8b1b-016711c2fd07 /               ext4    errors=remount-ro 0       1
# /boot was on /dev/sda1 during installation
UUID=f3e58f86-8999-4678-a5ec-0a4b621c6e37 /boot           ext4    defaults        0       2
# /home was on /dev/sda9 during installation
UUID=bcbc1c4d-46a9-4b2a-bb0a-6fe1bdeaed22 /home           ext4    defaults,nodev,nosuid        0       2
# /tmp was on /dev/sda5 during installation
UUID=8538eecc-bd16-40fe-ad66-7d7b9287839e /tmp            ext4    defaults,noexec,nosuid,nodev         0       2
# /var was on /dev/sda6 during installation
UUID=292696cf-fc15-40ab-9cd8-cee9bff7e165 /var            ext4    defaults,nosuid,nodev         0       2
# /var/log was on /dev/sda7 during installation
UUID=fab1f85b-ae09-4ce0-b169-c01205eb8f9c /var/log        ext4    defaults,noexec,nosuid,nodev        0       2
# /var/log/audit was on /dev/sda8 during installation
UUID=602f5003-4ac0-49e9-99d3-b29378ce9430 /var/log/audit  ext4    defaults,noexec,nosuid,nodev        0       2
# swap was on /dev/sda3 during installation
UUID=a538d35b-b2e9-47f2-b72d-5dbbcf0afca0 none            swap    sw              0       0
/dev/sdb1               /mnt/usblpsc                      auto    noauto,user,rw,noexec,nosuid,nodev   0      0
/dev/sdc1               /mnt/usblpsc                      auto    noauto,user,rw,noexec,nosuid,nodev   0      0
/dev/sdd1               /mnt/usblpsc                      auto    noauto,user,rw,noexec,nosuid,nodev   0      0

sudo users are not able to paste executable files in /bin into the file system which have the noexec option set. But limited users are able to paste the same files into the file system which have noexec option set. Why is it so?