Because of the high ridges, less than 1/4 of the meat surface is in contact with the pan surface. This slows the transfer of heat from the pan to the meat.
You could grill mark both sides with the burner on a higher temeprature then turn it down until it cooks through, or,
Make your grill marks on both sides then pop the whole pan into a 350 F oven to finish cooking. The wood handle will be OK in a 350 F oven. It may darken over time.
I prefer to sear the meat in a regular skillet (CI or SS) and finish it in the oven (at 400 F) if it's a thick steak.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan