Your statement is 100% incorrect. The TTK requires more factors than DPS does. Specifically, it depends on the kind of target and (in many games) where you hit that target.
Your pistol is going to have a drastically different TTK against Rhino than against Aura.
“Damage Per Second”, on the other hand, counts only what is flying through the air, before calculating what defender-specific factors may come into play.
except that TTK is more exact and DPS is more of an average.
Whenever TTK is derived from DPS, it embeds all the same uncertainties and guesses and is no more exact.
If your DPS assumes X% of bullets hit, then your TTK is also assuming X% the damage applies.