On the BMW build configurator non-runflats plus a spare are listed as an option on the X1. There are handling packages on many models that come with non-runflat Michelin Pilot Super Sport tires.

On the MINI configurator runflats are listed as an option for 16" wheels on the non-S hardtops, convertible, and clubman.

"16" x 6.5" alloy wheels in our Silver Loop Spoke design with a silver finish. Equipped with 195/55 R16 performance tires. Please note: All-season Run-Flat and performance Run-Flat tires are also available as a no-cost option."

So it would appear that the early non-S hardtops with 16" non-runflats was not a factory mistake.