Just to preface, I’m actively trying to not be the “well, ackshally” guy. I’m just really passionate about potatoes and potato education. Really just science education but potatoes are science, dammit.
The part you quoted, when in the context of the rest of the post, describes how boiling them whole specifically allows you to leave them in the pot without them getting soggy. You can leave them in there for an extended length of time as the amount of water they’ll absorb relative to their total volume is minimal due to the low surface area to volume ratio, plus the intact skin severely reduces the rate of water absorption.
Here’s where the well ackshally avoidance part is important. I have an MSc in botany, so I took a lot of plant physiology courses, plus I wrote a paper about this as a “fuck you” response to a stupid assignment by an asshole professor. The following is a crash course on potato science, no one is under no obligation to read it.
It’s not overcooking itself that causes soggy taters. When you cook a potato, the starch absorbs water and swells. When you cook a whole potato, the amount of water available is rather limited as potatoes are low moisture tubers, so the starch can only absorb as much water as is available in the tater itself. When boiled whole, the periderm (skin) maintains the structure of the potato, keeping it from breaking apart, and limits the amount of water that can be absorbed into the pith, the starchy interior. The latter is actually one of the primary natural functions of the skin. The total moisture content of a boiled whole potato is shockingly close to its raw state. Don’t believe me? Weigh a few whole taters using a decent scale, boil them for an hour, then weigh them again. It’ll be damn near the same. That’s one of the perks of cooking them my way - I can add more milk and butter without them getting soggy.
When you cut potatoes up, the starch can maximally swell as it has practically unlimited access to water, plus vastly more surface area, increasing the rate of water absorbtion. Since the skin no longer maintains the shape of the potato, small fissures appear as the structure of the pith begins to degrade. These further increase the surface area, consequently increasing water absorbtion even more, which further increases pith degradation. It’s this excessive water absorption by starch that leads to a gluey consistency and being cut up facilitates absorbtion through these mechanisms. This is also why wax potatoes are more resistant to falling apart than floury potatoes when boiled, as the starch content of a wax potato is much lower. Side note: I actually prefer a 1:1 ratio of wax to floury potatoes in my mash.
A way to test and verify is to boil up some spuds using your preferred method and mash them as normal, but add a fair bit more than normal of hot water, milk, or another primarily water based liquid, i.e., not cream or butter. You’ll end up with a gluey tater paste.
ivanafterall