No, the last number in the sequence of 245.60R-18 signifies the size of the rim?wheel the tire will fit on. For those tires you need to buy 18" wheels or buy 20" snow tires for the stock rim size.
The first number, 245 is the tire width, the second number 60 is the aspect ration, R indicates it is a Radial Tire, and the last number 18 is the rim diameter. This explains how to read the markings on tires.
If you are asking can you downsize from the Touring standard 20 inch wheels and tires to an 18 inch tire and wheel as your topic header states , then yes you should be able to. The 245X60X18 is an optional factory installed size put on the LX, EX-L, and EX 2019 models. Should be the same for the 2020? I believe many owner's put the smaller sized wheels and tires on for winter tires.
Should be no problem what so ever. Here is a comparison of the two sizes.