Will I just need to HTFU and get used to weight-bearing on my shoulders?
Yes, but it gets better once you start trying; the equal and opposite reaction to pedalling torque tends to lift you off the bars. Some people report a different sensation of weight bearing when switching from road to turbo, even on the same bike and properly levelled. It's possible that the wind load on your body also has an effect, even at only 25mph; the torso is probably a lifting body for most people.
Yes, but it gets better once you start trying; the equal and opposite reaction to pedalling torque tends to lift you off the bars. Some people report a different sensation of weight bearing when switching from road to turbo, even on the same bike and properly levelled. It's possible that the wind load on your body also has an effect, even at only 25mph; the torso is probably a lifting body for most people.