Is it true that tomato paste thicken sauces?

My husband and husband`s mother try to make me believe that tomato paste exist to thicken sauces (when your spaghetti sauce is too liquid, they say, you just add tomato paste, it is so thick that it will `absorb` the extra water and makes it thicker!). I think it is ridiculous, and I do believe that tomato paste is to add some tomato and acidity flavor to your sauce and that is all, not to change the texture of your sauce. Please help. I am wrong here?