It is impossible to discuss 6.88d2 without acknowledging its historical timing. In December 2016, Valve released patch 7.00, the "New Journey," which fundamentally changed Dota 2 forever with the addition of Talents, Shrines, and the Map Rework.
The "d2" in the title refers to the specific build of the map file. Custom maps are notoriously prone to memory leaks and game crashes. dota lod 688d2 new