Statistic "average_linear" does ignore "keep_last_sample"

Why the hell does the statistics sensor ignore the setting “keep_last_sample = true” when the method “average_linear” is used? Not every sensor does deliver periodic values especially when the value does not change much. (like a washing machines current that is 90% of the day zero but when it runs it changes)

How can I solve that without adding the next filtering sensor just because the statistics one seems to be buggy. Or do I miss something?