The old BW's were the Cume after a specific weekend (ie..Presidents Day or Labor Day)
The new version gives every BW a fixed length of time. The old ones wer not the final domestic gross as some of the underlying movies stayed in release past the BW/HW cash out date.
Another point is that the business has evolved. Last year FAST5 premiered the end of April and did not "qulaify" for a BW and was one of the biggest movie of the year. RSAPE premiered Aug 5 and did not get a BW. CBALN premiered the week before, had an optimistic strike of 120 (Hah!) and
But THELP opened Aug 12 and would NEVER have had a BW. In the new system, it would have had one in the 2nd or 3rd week when the real potential box office total was known.
One last example is PUSNB which was the first of the new BW's In the old system, once again an Oct 26 release would not have had a BW, and in the end we had a nice profitable BW.