Not range.getCounts([Feature.DateFormat]): that counts the FORMAT alone — a blank cell or a
text cell carrying a date-category format counts there too, which is the wrong, looser
condition for "how many of these are dates". DateFormat is deliberately just a formatting
predicate now (see ICellRange.Feature's own remarks); this is the value-level question a
report asks instead, composed from public API rather than any single feature.
How many cells in
rangeare genuinely dates — numeric value AND date-category format, read directly off each value the same waygetInteropType()already classifies it for display.