While setting IFS=$"\t\n" may make problems less likely when strings contain spaces, it's still not correct. File names (and other strings) can contain tabs and newlines, too. That's relatively rarer, but the quoting approach always works.
#!/bin/bash
items=(
'a'
'b c'
"d\te"
"f\ng"
)
echo "Unquoted:"
for item in ${items[@]}; do
echo -e ". $item"
done
echo "Quoted:"
for item in "${items[@]}"; do
echo -e ". $item"
done
set -euo pipefail
IFS=$'\n\t'
echo "Unquoted strict mode:"
for item in ${items[@]}; do
echo -e ". $item"
done
Unquoted:
. a
. b
. c
. d e
. f
g
Quoted:
. a
. b c
. d e
. f
g
Unquoted strict mode:
. a
. b c
. d e
. f
g
(GNU bash, version 4.2.37(1)-release (x86_64-pc-linux-gnu))