I would argue that defense is mostly effort period.
There are scores of examples of NBA PGs who are horrible on defense but are starters and even All-Stars because of offense. I will let you tell us the ones who meet these same criteria because they are very good defensively or just have good measurables, but are not good offensively.
There 10 million Alexander's with great measurables that will never sniff the league because the #1 job of every PG is to run the offense - not the D.
You're right, there's a ton of 5'11" PGs with average athleticism in the NBA.