@David Song T-11 is plywood. The Masonite type siding OP has is called, I believe, hardboard. The replacement material, smartside, etc is resin impregnated and quite durable. The older hardboard is still holding up/performing in drier climates when installation was good, eg no nails overdriven and z flashing used where needed, and it was kept caulked and painted, including the seams, window trim and paint on the lower exposed edges and it was installed a distance from the ground. The lack of gutters and the short roof overhangs don't help. No doubt it was a poor product and newer, better materials are available today. Looks like OP has a poorly done repair to a product that easily deteriorates when not properly installed or maintained. As siding mainly protects the house framing, it is pretty important to identify where water can penetrate the building envelope and repair it sooner rather than later. Sometimes caulk, patching material and paint will allow you to kick the can down the road, but not if it is flashed wrong. You have to keep water out.