Hi James,
It is not a bug.
Happened to come up in today’s meeting with Lance:
Actually Lance coded the base plugin so the basic slplus shortcode , if someone puts in ALL caps redirects (renders behind the scenes as lower case)_ so that works with either capital letters or lower case letters, but shortcodes with attributes need to be in lower case.
Once upon a time , people who are not familiar with the WP shortcodes codex and rules were writing in to say SLPLUS is broken because they used all caps . All shortcodes in WP are lower case.