Problems encountered with printing local variables in the new command substitution in bash 5.3

The test code is as follows:

test_case5 ()
{
    echo "test_case5 ret----------"
    local a=1 b=2
    local -n c=a d=b
    local all_var_info=$(local)
    declare -p all_var_info
}

test_case6 ()
{
    echo "test_case6 ret----------"
    local a=1 b=2
    local -n c=a d=b
    local all_var_info=${ local;}
    declare -p all_var_info
}

test_case5
test_case6

The result is that the variable substitution for starting a child process
in the past could produce the printed value, but the new one cannot.

test_case5 ret----------
declare -- all_var_info=$'declare -- a="1"\ndeclare -- b="2"\ndeclare -n
c="a"\ndeclare -n d="b"'
test_case6 ret----------
declare -- all_var_info=""