Correct: the "10 second rule" refers to time between the espresso finished brewing and serving to customer. This is to ensure the cup quality is delivered to the customer. Letting the cup sit around, negatively affects the aroma, crema and taste.
The leading authority on espresso quality may be the WBC. World Barista Championship standards for brew time are 20-30 seconds for a 1 ounce espresso shot.
Short extraction times llike 13-17 seconds usually result in a weaker, under-extracted shot with less crema. The crema is also usually made up of larger bubbles compared to the tiny bubbled, micro-foam, denser, more viscous crema found on a well brewed espresso. Frequently the short-time shot is also plagued with 'blonding' problems and a sour or salty taste. A 'short-time' shot is not a ristretto, which is a properly prepared shot run less than standard fill level - in slightly less brew-time than standard.
Although different machines, baristi, coffees will all behave slightly differently, a 13 second shot is not destined to win a taste quality comparison with a properly prepared espresso. Super-automatic machines and chain operators are frequently calibrating to a compromise between quality and machine reliability. They are also frequently operating within the design compromises involved with grinders/brew chamber dimensions/tamping mechanisms/multiple dose ranges/multiple brew levels/maintenance/service costs - just to name the key factors. They often settle on standards that are less than ideal for cup quality - in favor of other factors. Usually the super-automatic operators only allow the staff to adjust the grind settings - not the other brew parameters such as tamp, pre-infuse, water temp, water flow, grind dose time.
Enough prattle - time for an espresso!
By the way, love to hear your opinions regarding both La Marzocco and Super-auto shots and milk foaming.