I would saythose are two different cases.
If I understood codex correctly and didn’t miss anything, meta_value and meta_value_num are valid values for orderby, but using meta field name / key directly isn’t. You would need to add the field name as meta_key parameter to the query args.
orderby defaults to date which I think might cause similar results for the two setups.
Related codex entry https://codex.wordpress.org/Class_Reference/WP_Query#Order_.26_Orderby_Parameters
If meta key is a valid value for orderby, then that is something new to me. Thanks!