Hey, just so you know, Steam doesn't track playtime for DLC apparently, only the main game, hence why it shows 0.0 hours played for Rimworld Biotech. From what I gather, for rimworld and, I imagine, most DLC, it's because the DLC is dependant on the main game to run. I imagine it's simply not a priority to change it since at most it simply causes people to post "0.0 hours played" on DLC reviews :P

I actually have almost 1700 hours of rimworld via steam and 40 hours played in the past two weeks, and maybe another 20 between then and the 22nd when I purchased it.