Icarus,
No, the point is the ATC required fix time does not change, but the aircraft's estimate of crossing the fix does - eg when it's all crosswind and the runway changes from 21 to 03, suddenly your profile through julim changes from about 10,500 to 19,000 feet - descent point moves about 25nm downtrack, you are at much higher TAS for much longer, so your estimate moves forward by up to 3 minutes. Now you and everyone else have to slow down to still meet the arbitrary julim requirement even though everyone is in the same boat and the spacing is still the same.