On your referred web site, Example 3 is the optimum set up.
It must be an older web site as it has only 8 rear cogs when the norm these days (for road bikes) is 9 or 10.
Following the gearing pattern you would go through the gears in your smaller chain ring and go from the small chainring (39t) to the large chainring (53t) and you change your combination from 39/16 to 53/21 then your next change would be to the 39/15.
Unless you are mentally plotting your upchanges or have a gear indicator this appears to be a laborious exercise of double shifting and running the risk of dropping a chain.
If it was a 9 or 10 speed system I would have the 16 rear cog included and this cog would make double shifting unnecessary.
I would not have double shifted anyway unless I was on a long gradient which that gear totally suited. Also there is an efficiency loss in that cogset by going to a 53/21 as you are opening up the chain angle.
In all my years of road racing I have never seen or heard anyone double shift from the small ring to the big ring and back again just to pick up a gearing sequence. You would just live with the gap.
Only experience will tell you when to shift.