It's way more complicated.
Take an extreme example:
Let's say you cross a ciliolare ( acid loving species) with a hangianum (limestone loving species). When you flask the progeny, you make the seed sowing at pH 5.5 or 6.8, with or without calcium, the seedlings that grow 'well' will not be the same in all cases... When you grow them in the nursery, if you do not use lime and grow the plants in fern roots, the plants that favors ciliolare for the acid-loving habit will grow well, the others sulk. If you grow them in limestone chips, the ciliolare-style will sulk, and the hangianum style will grow. Now we do not know anything about heredity, so it is possible that the genes are transmitted as a package, like lime adaptation and fragrance for hangianum.It is very simplistic and not accurate, but it's a concept that has been proven.
Now, with the complex hybrids, if you use a lot of lime, you will favor progeny that have certain traits, if you don't you will favor others seedlings. In both instances there will be very good growers, and very poor ones, but not the same plants.
As an example, with Lippewunder, plants from the original crosses perform very well in Taiwan and Japan. Gorgeous plants grown in Germany, that have been bred 2-3 generations further (Lippewunder x Lippewunder, and again and again), die quite quickly in both those countries, side by side with great clumps of original Lippewunder but are easy to grow for US people. As a fact, it is very difficult to grow vintage complexes and the latest generation of Lippewunder. The latter, through selection in another German nursery that grew them in a very different way from the original ones, flasking, and further line breeding, have very different nutrition and pH requirements. The f1-f2 Lippewunder can grow in pure sphag moss, the f4-f5 cannot. All are gorgeous plants if grown properly, but they cannot be grown together without specific adjustments for one or the other group...
That's what I call unwanted selection, and explains too why crosses with the same parents, done at different times, hence with different TC media and growing conditions afterwards, do not give the same result. The runts of each nursery are not the same for the same cross with the same cultivar.
It has been studied commercially with phals and with odonts. This explains too why the f2 f3 plants of many species perform 'better' than wild plants in cultivation, but this explains too that maybe we have lost a lot of potential, and growing oddities in cultivation in term of nutrient, light, temperatures requirements.
That's why I would agree with Guido that 'linebred' species or art propagated species, after a while are not 'species' anymore...
Add to that that maybe in the f4 f5 of some species, some people had added another species to make the result more attractive like many concolor, godefroyae, spicerianum, insigne, stonei, glaucophyllum, primulinum... that have a percentage of another species, but look like an improvement over the wild plants, or extinct plants like callosum 'Sanderae', lawrenceanum 'Hyeanum', curtisii 'Sanderae' that no longer exists and are represented by lookalike hybrids in cultivation today masquerading under the species names.
I know as a fact for having selfed and sibbed some godefroyae, lawrenceanum 'hyeanum' etc... that they are not species, but hybrids. For lawrenceanum and callosum it was easy, people selfed Maudiae 'Magnificum' and selected progeny looking like lawrenceanum or like callosum. Unfortunately, selfings of those plants will suddenly make a few progeny that is not 'right'. Like the callosum sanderae around in Japan. When selfed, suddenly there will be few plants with flat symmetrical dorsal, horizontal petals, and leaf mottling of lawrenceanum. Very few, but enough. Many leucochilum selfings and siblings from Thailand will suddenly throw out a few seedlings with heavily mottled, wide soft leaves typical of bellatulum. Eventually when bloomed they will have spots like a bellatulum. After many generations of 'breeding' if the species has been contaminated by another species in the early generations, it is not a species anymore, forever. That's why what we are doing in cultivation 'species propagation' is only for artistic purpose, but never for any 'conservation' purpose. We cannot guarantee species purity in cultivation, that's very clear...