yes, your second thought is true.. plants are no different than people when it comes to exhibiting the traits of the parents.. i'm sure if you have any brothers and sisters, you both may have some similar traits, you also have some different ones.. you may have your mom's eyes, while you have your dads nose.. since genetics from both of them are present in you, you have to chance of any or all of the traits coming out in you.. same as plants..
some seeds may take on the traits of the mother plant, be it for ex. a long flowering period, and sativa type of leaves, or they could take on traits of the father plant, short flowering, and more indica type leaves..
this is where a good breeder is worth his weight in gold honestly.. back crossing, and knowing what traits to look for and which ones are gong to get passed on to the offspring are super things to know, and not so easy most of the time.. they usually have to grow out large numbers of plants in order to see some of the more recessive traits that can and do pop up from time to time, and then pick the siblings that display the charecteristics that they are looking for. then pick those siblings, breed them together again, and start the process all over again.. it's usually considered to be a stable strain once it gets taken to like the fifth or higher generation, f5's...