We are talking past each other.
I did read the paper cited and it doesn't address the problems of genetic drift which is why I do not recommend using simple table sugar to propagate the yeast. Its simply elucidating the methods of metabolism control in yeast not addressing whether genetic drift will occur. I can post papers about the lac operon in E. coli if you want and they would only be marginally less relevant to my objection to using table sugar. Genetic drift, bottlenecking and founder effects are real and well studied.
Removing a selection pressure only increases the likelihood you will get a completely different strain out of your harvest. If 10% of the population in that bottle have a mutation that makes them grow faster on table sugar they will dominate each successive generation and after the necessary rounds of propagation needed for harvest, you will end up with nothing close to what Sam Adam's uses. Sure the yeast will likely still maintain the ability to ferment beer but that is not the goal of harvesting yeast. The goal is to get the same yeast not just any yeast.
So again I will ask you, if your goal is to harvest as genetically close of a strain to the Sam Adams strain why would you propagate them in a different environment than what they are utilized for? If I was looking to harvest a strain of yeast that I really liked for my beers I wouldn't go propagate them in apple cider, I'd keep them in beer.
I am fully aware that yeast have the ability to utilize both simple and more complex sugars and that upon exhaustion of one they can switch to another.
That is not my point of contention so papers on how yeast control their metabolism are borderline irrelevant.
Founder effect
Population bottleneck