This is a topic I am interested in.
A somebody that has struggled to get solid mouthfeel in beers, based on my experience and reading I am fairly confident that the standard "low mash temp = thin/dry beer; high mash temp = thick/sweet beer" is false, or at least not that clear cut. If you like Brulosophy, they have a few experiments on this topic.
The thing that most people overlook is that alcohol adds sweetness and body to a beer. In the case of mash temps, the higher alcohol of the lower mash temp beer mostly cancels out the dextrins of the higher mashed beer. I plan on doing a few experiments on this myself to prove this to myself.
I actually have a split batch in kegs right now that was related to this topic. I split a 5 gal batch of Porter at fermentation time and added 10% table sugar ito half. My goal was to test a 5% beer vs a 6% beer. Unfortunately, I realized as the beer was coming to a boil that my thermometer was about 10F off and I actually mashed around 162F. So I have a 3% beer vs a 4% beer. I plan to get some input from my beer club on these, but I can pick out the 3% beer and it is thin and too roasty (not thick and sweet) and the 4% beer has better mouthfeel and balance. The OG on these beers was 1.052 and 1.060 with a FG around 1.030 (so actually 2.9% vs 3.9%).