He must have decided to employ the 3rd party service to determine his market timing since he admitted to botching the entrance back into the market after exiting during/prior to the 2008 financial crisis.
That was me - I got out within 7% of top in 2007-2008, but didn’t get back in till it was nearly entirely back. Adjusted for dividends I did exactly the market, although I suppose I slept a bit better.
3-5% works well as long as you have flexibility for a third deviation left tail event (cut back for a couple years, work part time, etc). I’ll be able to get away from a higher than 4% “withdraw” simply because my rentals generate 7% from their current equity value in cash alone (not including principal pay down or appreciation).