For future reference if anyone comes across this question, I did find a workaround that we can use. Our solution required duplicating row level data, but thankfully for our use case having a single duplicate for each row still provided acceptable performance. The key ideas were to use custom SQL to duplicate the data set, use "Show Missing Values" on a calculated date field to create the correct number of rows, self-blend to replicate the desired measures across all rows, then create the necessary inequality filters.
The attached workbook doesn't quite capture the exact process - custom SQL wasn't needed when working with sample data in Excel - but hopefully it can help someone struggling with similar issues.
If anyone can find a cleaner solution to this problem, I would love to hear it!
Binning Problem v2.twbx 37.2 KB