According to How to Brew, yeast can lose their ability to ferment maltose (from the malt) if there is too much simple sugar in the beer. The limit the author gave for sugar was 30% of the total OG for the wort. For five gallons, 30% is a whole lot of sugar. I added 2 pounds to some of my higher gravity beers with no issues (got 80% AA).Does JP actually say they lose the ability to ferment it, or that they just won't? Do you know the page by any chance?
I ask because it is very unlikely they lose their ability to ferment maltose. They may not ferment it to completion in that batch, but that's not the same thing as losing the ability to do it. If you took the yeast from that batch and fed it maltose I have no doubt it wouldn't have a problem. I grow yeast all of the time in 100% glucose solutions (well, 2-10% glucose, but it's 100% of the sugar) and they have no problems transitioning to starter wort.
"In addition to the lack of nutrients, wort with a high percentage of refined sugar (about 30%) may cause the yeast to lose the ability to secrete the enzymes that allow them to ferment maltose, resulting in a stuck fermentation." (Palmer, p. 86)
He does use the qualifier "may."