Keep in mind that these two conditions are present during landing, and this is not a problem
True. I recall landing a DC3 and the captain lambasting me for reducing power below 20" MP on final approach as he said it would damage the engine. He was one of the old school who had thousands of hours on DC3's but from his lack of knowledge of engine handling it was clear he had never bothered to read a book on the subject. There are mechanics around of the same old school.
Even with full flap down it was well nigh impossible to reduce to correct threshold speed because the old man in the left seat held his hand firmly behind the throttles. With excess speed we floated for ages with power still on and finally thumped down in three-points which DC3's don't take too kindly too.
I wrote to Pratt & Whitney to get the good gen on engine handling of the 1830 and the reply said that at the low indicated airspeeds in the circuit and on final, there is no chance of engine damage with low manifold pressure and rpm at 2050 or 2300 rpm. I showed this to the old bloke and after squinting at the document through his look-over glasses stuck on the end of his nose, he snorted with derision and threw the letter into the waste paper basket saying he had flown DC3's for decades and wasn't going to change his opinion on engine handling.