Originally Posted by cheshirecat

That reason being taking off from a dead stop.

Not all transmissions are built the same and the 370z does not enjoy being shifted into first while moving at anything faster than a crawl. The synchros yelling at you while they work to fix your technique should be a hint.

Anyway, as far as engine braking goes, it seems the transmission is stout enough to handle it without excessive wear and tear. As long as you are properly rev-matching, you shouldn't experience any issues.