With bundling turned on options beginning with a single '-' are treated as single character options exclusively. If you want to get the auto-abbreviation behavior of long names under bundling you must start the option with two '-'s. This is explicitly stated in the documentation.

Aaaah.... That explains the behavior.  So, if one wishes to abbreviate the 'test' option to t with bundling enabled, one must somewhat counter-intuitively use '--t' instead of '-t'.  This was not clear to me from the documentation.

I see, incidentally, that this remains true even with bundling_override set, which eliminates the double-dash requirement for long options, but evidently not for abbreviations thereof....