The two files you edited are symlinked to their counterparts in the FreePBX module webroot:
[root@freepbx etc]# ll /etc/asterisk/ | grep "features.conf\|extensions.conf"
lrwxrwxrwx. 1 asterisk asterisk 52 Dec 19 2017 extensions.conf -> /var/www/html/admin/modules/core/etc/extensions.conf
lrwxrwxrwx. 1 asterisk asterisk 50 Dec 19 2017 features.conf -> /var/www/html/admin/modules/core/etc/features.conf
you’ve altered FreePBX module files, which will probably trigger dashboard warnings of altered files, but more importantly will be overwritten when you update the core module. The only supported way to adding features is what you were doing first, as described in this post: