Yes, technically, you're putting more torque to the rear axle than you would normally be, but as several people pointed out, you're usually doing it on easier sections of trail, so I don't think that's an issue.
Even in 2HI, low gear on my sm420 is lower (more torque) than stock Lo/Lo. Combine that with coarse-spline axles, a welded diff, and a habit of running only in 2wd (for lack of PS) and I'm probably asking for trouble, but no problems yet.
For all the potential drawbacks, I think it's better than the driveline bind from maneuvering with the front axle engaged on any kind of tractive surface.
Even in 2HI, low gear on my sm420 is lower (more torque) than stock Lo/Lo. Combine that with coarse-spline axles, a welded diff, and a habit of running only in 2wd (for lack of PS) and I'm probably asking for trouble, but no problems yet.
For all the potential drawbacks, I think it's better than the driveline bind from maneuvering with the front axle engaged on any kind of tractive surface.