How do I populate an array with the output of a function that sets a global variable?

I have a shell script which calls a function that behaves differently based on the value of a global variable and whose output is a list of values that I want to store in an array.

I'm running into a problem because when I try to capture the output of the function using any variation of the obvious syntax:

mapfile -i the_array < <( the_function )

my global variable that's being set inside the_function reverts to it's previous value once the_function returns. I understand that this is a known "feature" of capturing the output of a function that has side-effects and I can work around it as shown below but I'd like to know:

1. What's the rationale that went into bash to make this workaround necessary?
2. Is this really the best way to get around the problem?

To simplify the problem, consider this case where I want the function to print 5 numbers the first time it's called and not print anything the next time it's called (this is the obvious syntax which doesn't produce the expected output):

$ cat tst1
#!/usr/bin/env bash

the_function() {
    printf '\nENTER: %s(), the_variable=%d\n' "${FUNCNAME[0]}" "$the_variable" >&2

    if (( the_variable == 0 )); then
        seq 5
        the_variable=1
    fi

    printf 'EXIT: %s(), the_variable=%d\n' "${FUNCNAME[0]}" "$the_variable" >&2
}

the_variable=0

mapfile -t arr < <( the_function )
declare -p arr

mapfile -t arr < <( the_function )
declare -p arr

$ ./tst1

ENTER: the_function(), the_variable=0
EXIT: the_function(), the_variable=1
declare -a arr=([0]="1" [1]="2" [2]="3" [3]="4" [4]="5")

ENTER: the_function(), the_variable=0
EXIT: the_function(), the_variable=1
declare -a arr=([0]="1" [1]="2" [2]="3" [3]="4" [4]="5")

That doesn't work for the reasons stated above and I can work around it by writing the code as (this one does produce the expected output):

$ cat tst2
#!/usr/bin/env bash

the_function() {
    local arr_ref=$1

    printf '\nENTER: %s(), the_variable=%d\n' "${FUNCNAME[0]}" "$the_variable" >&2

    if (( the_variable == 0 )); then
        mapfile -t "$arr_ref" < <( seq 5 )
        the_variable=1
    else
        mapfile -t "$arr_ref" < /dev/null
    fi

    printf 'EXIT: %s(), the_variable=%d\n' "${FUNCNAME[0]}" "$the_variable" >&2
}

the_variable=0

the_function arr
declare -p arr

the_function arr
declare -p arr

$ ./tst2

ENTER: the_function(), the_variable=0
EXIT: the_function(), the_variable=1
declare -a arr=([0]="1" [1]="2" [2]="3" [3]="4" [4]="5")

ENTER: the_function(), the_variable=1
EXIT: the_function(), the_variable=1
declare -a arr=()

but while that works it's obviously horrible code since it requires the lower level primitive to be more complicated than necessary and tightly coupled to the data structure being used to store it's output (so not reusable if a case arises where we just want the 5 numbers to go to stdout, for example).

So - why do I need to do that and is there a better way?