Ah! Options…we all love options…am I right? Why rush to a decision when you have the pleasure of choosing the best option at your own leisure? There’s a lot of variables in this world… and because of that, anything can happen…therefore, it is wise to assume variability! 
Because of variability, the option that you have chosen too early and in haste (Point-Based approach) might not be the right one overtime, and too late or too much to adjust/change! Preserve your options (Set-Based approach)…let these play out…some will drop off overtime…and one will remain at the end: the one true option!
The point: SAFe principle #3 — “Assume variability; preserve options”
I love this principle. It totally opposes the Phase-Gate approach (i.e. Six Sigma’s DMAIC (Define, Measure, Analyze, Improve, Control) toll gate approach). Phase-Gate approach has no place in the world of Lean-Agile! The ‘Lean-Agile with Phase-Gate’ phrase is totally oxymoron!
Moving away from this Phase-Gate approach to the Lean-Agile mindset is one of the hardest things to do during transformation to Lean-Agile. Phase-Gate approach picks an option too early and sticks with it all the way to the end…only to learn that the picked option is the wrong one (not the optimum solution)! Phase-Gate uses documentation (lots of it) as basis of milestones. Contrast that to Lean-Agile. In Lean-Agile, milestones are based on objective evaluation of working systems (SAFe Principle #5). Lean-Agile preserves options to allow the process of discovery, elaboration, learning and adjusting to take 
place … taking advantage of the ‘Fast, Integrated Learning Cycle/ Fast Feedback Loop’ (i.e. via demo) — see SAFe Principle# 4. This approach, overtime, will eventually reveal the one true option (the optimum solution).
SAFe principle #5, SAFe Principle #4 and SAFe principle #3 are all inter-related (these work best when they are applied together). Try this exercise: using your own experiences, try to correlate or anchor these experiences to these three aforementioned SAFe principles.
Here is mine, my personal observations, applying these principles: I don’t buy the first house that I see when I am house hunting … I explore the marketplace first! The TV show “House Hunters International” illustrates the point so clearly.
Another TV show, ‘The Bachelorette’, illustrates the point so clearly as well: the bachelorette got a lot of options (of men)… and at the end, after a lot of happenings, she picks the one true option… her one true love (it’s a TV show, so can’t be sure if it is REALLY the one true love; however, in this example, we assume that it is!).
You get my drift.
So… don’t ever rush to a decision… take your time … reveal everything by exploring … observing…experimenting…inspecting…learning…adjusting. Find that one true option: in the ‘bachelorette’ example, find that one true love… in the house hunting example, find that one true house. Assume variability. Preserve options!
Unless you are in love… you rush in… like the Elvis song, “Can’t help falling in love”:
Wise men say only fools rush in
But I can’t help falling in love with you
