all the seeds are hybrid seeds, period. Unless they existed at the beginning of time and have not been changed since then, they are a hybrid, the are the result of cross-pollination at some point in the past.
Those that can be planted and produce “true to form” meaning say a Cherokee Purple resulting in a cherokee purple, have been at some point selected, saved, planted, harvested, selected, saved etc for multiple generations (of the plant) until almost 100% grow “true to form”, that may have taken 20, 30, 50 “generations” to become “stabilized” Thus, technically they are a “stabilized hybrid”
Most of the problem with being able to save, plant and get the same thing comes from the seed you buying be a “first generation” (aka F1) hybrid. Not only are you unlikely to get the same thing from saved seed, but it may be patented and thus be guilty of patent infringement if you save and reuse.
Add to that the GMO’s which, unless you had to literally sign a contract to be able to buy, and it likely included a mandate to use certain chemicals, only purchased from the same company, you haven’t bought “GMO” seed, so unless something really new is happening, this is not a concern for your home garden.
Anytime someone says you “can’t” do plant this, or that, or “Can’t” compost x or y, they are likely overgeneralizing to the point of absurdity, or have no actual idea what they are talking about.