Well, that is true that it does give you more hit points, therefore making you "tougher". However, the fact that in only gives you 3 HP makes it a very weaksauce feat (thus the trap option where taking this actually doesn't make my character tougher overall since other feats would make me "tougher") and, in play means that you actually can't take more hits since 3 Hp is overshadowed by 2nd level.
When bad guys do about 10 HP/CR per round in damage, an extra 3 HP doesn't actually do much of anything. You still drop in one hit on average.
Then again, are you seriously trying to defend Toughness as a good choice for a character? Really?
I have a quicker way to say what you're trying to say: while it makes you tougher than you were, but it doesn't make you tough. Like platform shoes make Tom Cruise taller, but they still don't make him tall.