Slurm: All commands and options are case-insensitive, although node names, partition names, and reservation names are case-sensitive (node names "LX" and "lx" are distinct).

https://slurm.schedmd.com/scontrol.html#lbAD

PBS: Job attributes are case-insensitive.

https://pbsworks.com/documentation/support/PBSProUserGuide11.1.pdf#G7.808161

Therefore, on cheyenne.ucar.edu,

PBS_ACCOUNT=$(/ncar/opt/sam/sam_validate.py $USER | grep -m1 True | cut -d ',' -f 1)  #UCSU0053

source /glade/u/apps/ch/opt/usr/bin/getacct.sh  #ucsu0053

sacctmgr -P show assoc user=$USER  #ucsu0053

id -Gn  #ucsu0053

are all equivalent.