I believe it is ECM rifling. Of the newer guns, only my 625PC has cut rifling. If you are going to load 357 cases for it with lead bullets, I would use mild loads and softer bullets normally specified for 38 Special. Extra lube or coating would help. Mine are rated at 12. The pronounced leading I experienced was with the harder 18s, which you should expect would easily bridge the rifling profile and allow hot gases to surround the bullet.
It's not a deal breaker. Just know what you are working with. My 686-6 and 625 JM are the same way...generally unacceptable with bare lead, even with throats reamed and forcing cones recut. Castboolit fellas tell me how wrong I am, but that's not helpful. I don't cast my own. My 625JM was replaced with a 625PC because Jerry Miculek wanted to switch to lead bullets and asked for cut rifling. It's so obvious how problematic ECM rifling can be.
This smaller 60 Pro in the hands of a reloader is a perfect opportunity to use X-treme's plated bullets with their crimp grooves. To use 357 brass just stay somewhere between 38+p and 357 Mag minimum.