Anyone see the flaw here?

Yes, unless I misunderstand your intention. If the last sale date were 2018-01-02 then it would say "OLD" - it doesn't make a lot of sense to me that only records with a specific last sale date of one day would be considered current. You might just need to change the formula to {lastsaledate}>(TO_DATE('2017-12-31', 'YYYY-MM-DD'))