PM for a narrow body game is indeed loaded. Loaded with things that ex williams engineers had been told not to do. Since the super pins were done by the time it was released, this would have had the most features at the time.
My understanding is the super pins all had a similar BOM, but its weird to see TZ voted by so many. JJP's Bom hasn't radically changed for its widebodies over the years. What they focus on putting in does seem to have changed.
BR is a very odd choice, yes there is the upper pf, but the lower is barren. More expansive than other system 11's, but it had no toys or tricks on the lower pf in part to cut down on cost.
The poll as a whole seems odd. It doesn't define what the eras are. There isn't any real great criteria. The original BK kicked off multi level playfields. The super pins had a similar bom and no one touched williams in that dept (compare BF to STTNG since it is based off it).
The problem is the way this is done its less about what had the most features/highest bom for its time and more is what is the most popular game with a ton of shit in it.