... the same array isn't working in qw same like the first one above?

They're not the same. "ABCGE ABCGE" produces a single string consisting in two alpha sequences separated by a space. qw produces groups (update: i.e., a list of zero or more) of non-space characters.

Win8 Strawberry 5.8.9.5 (32)  Mon 11/29/2021 17:10:24
C:\@Work\Perl\monks
>perl -Mstrict -Mwarnings
use Data::Dumper;

my @t1 = ('ABCGE ABCGE', 'ABCGE FGCGB', 'ABCGE JHAGT');

my @t2 = (
    [qw{ABCGE ABCGE}],
    [qw{ABCGE FGCGB}],
    [qw{ABCGE JHAGT}],
);

print Dumper \@t1;
print Dumper \@t2;
^Z
$VAR1 = [
          'ABCGE ABCGE',
          'ABCGE FGCGB',
          'ABCGE JHAGT'
        ];
$VAR1 = [
          [
            'ABCGE',
            'ABCGE'
          ],
          [
            'ABCGE',
            'FGCGB'
          ],
          [
            'ABCGE',
            'JHAGT'
          ]
        ];
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