Why doesn't the folder path (public_html to public_shtml) change when I add the ssl-certificate in the VestaCP panel?

Question

I add the certificate in the VestaCP panel, I restart Nginx but in the configuration file /home/admin/conf/web/%domain%.nginx.ssl.conf

still the same root /home/admin/web/%domain%/public_html;

although in the template

/usr/local/vesta/data/templates/web/nginx/php-fpm/default.stpl

exactly root %sdocroot%;

in the bash script that changes this

usr/local/vesta/func/domain.sh

I found

# Update web domain values
prepare_web_domain_values() {
    if [[ "$domain" = *[![:ascii:]]* ]]; then
        domain_idn=$(idn -t --quiet -a $domain)
    else
        domain_idn=$domain
    fi
    group="$user"
    email="info@$domain"
    docroot="$HOMEDIR/$user/web/$domain/public_html"
    sdocroot="$docroot"
    if [ "$SSL_HOME" = 'single' ]; then
        sdocroot="$HOMEDIR/$user/web/$domain/public_shtml" ;
    fi

But I never figured out how it checks "$SSL_HOME" = 'single'

Thank you so much in advance for the answers!