Their are multiple forms of dryland training that help hone and tone the body for downhill, cross country, and telemark skiing. I was a competitive ski racer, and inline skating up and over mountains in Colorado as well as along the bike paths, and using my Inline Slalom Gates all provided adequate training. Others who choose to ice skate have found benefits there as well.
Downplaying, or even disputing, the ability of any experienced, well trained inline skater to hold an edge on pavement while skating downhill at speeds of 30mph isn't necessary. We all have our own preferences, and sharing our skills is more effective than arguing over which method is best.
I own a double set (red and white) of Inline Slalom Flex Gates, for downhill slalom training/racing. I purchased them in 1994, and am interested in selling them. I live near Aspen, in Glenwood Springs, Colorado. There are 20 gates total (split between the two colors), and include the bases, epoxy, epoxy gun, and release "donut". I've included a photo of me using them back in the day.
I also have videos from ISRA (Inline Slalom Racing Association), which show a team up near Seattle using the gates for training and slalom races.
The women's Pro Ski Tour used them, as well as members of the Copper Mountain Ski team, all back in 1995.