The only potential problem you can run into with sync chain tension is having it too loose, which could lead to an unintentional derail / drop of the chain at an inopportune time.

As far as getting it too tight, you would have to use a breaker bar on the eccentric to put the chain under anything that comes even close to the amount tension that your average captain generates through the pedals on a normal ride, never mind on strenuous double-digit climbs.

Bottom Line: Close enough is good enough as long as there isn't too much slack.