Why does the "tcsh" behavior changed for Red Hat Enterprise Linux 6.8 ?

Issue

• The updated tcsh-6.17-35.el6.x86_64 in RHEL-6.8 does not behaves like the RHEL 6.7 version (tcsh-6.17-25.el6_6.x86_64)
• There seems to be differences in more ways than one, below can be the easier to reproduce :

Using tcsh-6.17-25
$> set myvar = `\echo "1 2 3"`
$> echo ${myvar}
1 2 3
$> echo ${myvar[1]}
1
$> echo ${myvar[2]}
2

Using tcsh-6.17-35
~]$ set myvar = `\echo "1 2 3"`
~]$ echo {$myvar}
1 2 3
~]$ echo ${myvar[1]}
1 2 3
~]$ echo ${myvar[2]}
myvar: Subscript out of range.