But a thinner mash would not result in more solubilized starch would it? So your presumption is that a thicker mash means oversparging (given that the same total amount of water is used for strike/sparge in the thick and thin cases).
Sorry for the slow reply, It's been a brutal week at work... Anyway,
Yes, for some brewers, thinner mashes may
result in more starch gelatinization, which is synonymous with more solubilized starch. But, yes, mashing thinner is not required to get 100% conversion efficiency, but it helps a lot of brewers who are having trouble getting good conversion efficiency.
No, I'm not presuming that a thicker mash means oversparging. What I'm trying to say is that, without measuring your conversion efficiency, you don't know whether you are achieving the efficiency through good conversion or strenuous sparging. Generally, pushing gravity higher by sparging would be considered less desirable than by conversion.