I will take you ideas under advisement but I am pretty sure that my tomato plants will not grow avocados or watermelons on them at any time in the foreseeable future. And if all that was necessary for a vegetable verity to be considered an Heirloom variety was for it to be open pollinated then every commercially grown GMO crop would qualify for Heirloom status because from sweet corn to orange juice all commercially produced GMO food items are open pollinated.
Here is a snippet of info from that Wikipedia thingy that you have so much trouble believing or understanding, but I can assure you that this sight's information about Heirloom, aka Heritage tomatoes or inbred tomatoes is correct. and the information on hybrid lines is also correct. I didn't say that the Wikipedia thingy was expansive knowledge but that it was a good sound primer on Heirloom tomatoes and most other self fertile plants who don't sleep around.
The red and bold red text below was added by myself to guide the reader to a better understanding of the subject.
"Heirloom seeds "
breed true,"
unlike the seeds of hybridized plants. Both sides of the
DNA in an heirloom variety come from a common stable cultivar, in contrast to hybridized seeds, which combine different cultivars. The hybrids exhibit "
hybrid vigor"
in the first generation, but the second generation tends to exhibit many undesirable recessive traits. Heirloom tomato varieties are "open pollinating", but cross-pollination is very rare without human intervention.
Heirloom seeds can be easily collected
and will continue to show the traits of the original seed because this family of tomatoes almost always self-pollinate. Collecting heirloom seed is as easy as picking ripe tomatoes, chopping or mashing into a jar till less than half-full, filling with water, shaking from time to time and allowing to decompose for 1–6 days until seeds sink to the bottom, then rinsing until the seeds are clean, and drying. This decomposition is beneficial because it discourages transmission of diseases to the seed, the drying promotes better germination, and because the seeds are easier to separate when they are clean.
"
http://en.wikipedia.org/wiki/Heirloom_tomato
.