No they won't have the same properties. Sometimes the seeds are just plain infertile, but at best the fruit randomly scrambles back to a non-optimal generation. A Heritage seed will produce the same fruit, generation after generation, a Hybrid will never produce a fruit comparable to its original cross and will produce, if it produces at all a inferior product to a Heritage seed.
A Jackass is a Hybrid horse/donkey. It is stronger than a horse and larger than a donkey. It is also sterile. Plants run the same way. Most times they are not sterile, but a lot of time you might wish they were.
To top it off, a hybrid seed is optimized for commercial farming, they look great, you can pick them early and they hold up under shipping well. They produce far more fruit than a normal plant and some times, around 6 or 7 on the list of desirableness is the heading taste. Never is nutrition on the list because our science is not advanced enough to understand nutrition.
A hybrid for hundreds of years has been selected to be healthy, disease resistant, reliable, tasty and easy to raise for food. That is why Heritage seeds HANDS DOWN taste better and smell better than Hybrids. Cross breeding plants works good on a short term view, but in the long run, bites ya on the rear.
It is now suspected that the trace proteins of organic soil has a lot to do with nutrition, not just smell and taste. And why not? The components that make up smell and taste are highly complex proteins. Hard to synthesize from NPK fertilizer. It is suspected that is why chemically grown foods loose their taste after a few generations of soil usage with chemicals.
So for those who think of gardening as a way to survive the depression or the end of the world, you should NOT use Hybrid seeds.
You may be confusing hybrid seeds with GMO seeds. Hybrid corn is made by crossing corn with corn, and is not analogous to a mule made by crossing two species (that’s how we know they are two species: if they were the same species, the offspring would be fertile).
Heritage seeds don’t breed true in general either, and for the same reason. Unless a plant is homozygous for all expressed traits and is pollinated only by other plants with the same genome (at least on the part governing expressed traits), it won’t breed true any more than a hybrid will. One doesn’t notice it so much with heritage seeds as they have always produced a variety of phenotypes instead of the uniformity found in commercial hybrids that makes not breeding true so obvious in their case.
I stand with you in objecting to any attempt to stamp out heritage seed lines, but for a different reason: basic population genetics shows that genetic diversity is necessary to the long term health of a population (in this case of some plant we grow for food). A strain of some rust or blight particularly adapted to attacking whatever Monsanto is hawking would be a disaster for the food supply if the only seeds available are the ones Monsanto is pushing.