Order the Kenpo 2000 Manuals (www.kenpo2000.com) to see what the Forms teach.
Forms teach Angel Changes, Gaseous Movement, Timing when dealing with more than one opponent, Moving Blockades, about Critical Distance etc. Dealing with more than one environmental variable at once needs new ideas to deal with them.
Extensions... right point - therefore Extensions changed to Formulations... see Brown 1 thru Black 3 Manuals Kenpo 2000 (www.kenpo2000.com). Extensions where changed to Formulations in 1988 (as was Long Form #7 created, and Knife Set #1, and Long Form #8).
The Formulations add new ideas like Working a Downed Opponent, Words of Motion to sophisticate the Art etc.