Let me clear it up for you NEWBS.It depends on what your definition of on the ground is.If you are trimming a blowdown with it and you have to cut at face level the top handle is surely safer than using a standard handle saw.
I confess that I might be one of the 'NEWBS' here! I have only been running a chainsaw since 1973 and keep learning more and more about them. But I try to never work with a chainsaw near my face.
Not above chest height it aint!And I cut wood for 36 years.
I think Lonewolf has pointed out something I never realized before. Holding a well balanced top handle saw at chest height and above with your left hand on the cross bar and your right hand on the top handle is much more secure and safe than doing the same with a rear handle saw.
I disagree with both of you guys here. I am not a climber, I don't work in trees, and understand why
lone wolf would be reluctant to use his 440 hanging from a rope - just the inertia of that thing kicking on could knock you off of a perch. But I have cleaned up a lot of blow down and storm damaged stuff. I would much rather have a conventional saw with a longer bar to reach up to these branches, than have to extend my body up that high with a trim saw.
There are several threads on A.S. where members comment on the value of a longer bar being reach, aside from being able to cut larger diameter wood. Biomechanically, you only have about 1/3 the strength when working with your hands above your shoulders than when they are at mid torso, in addition to being off balance when working with your hands overhead. Neither is good for running a saw. At some point, you should switch to a pole saw if the work is that high, or cut the branches off at a lower point and section them up when on the ground.
As far as kickback is concerned it's the same exact principals with the big saws...
It's not.
Even if you are holding your one-handed saw with two hands, six inches apart, you have half the leverage to resist kickback than when holding a conventional saw with two hands spaced 12 inches apart: think of your forward hand as being the fulcrum. You are also better balanced by having your arms spread farther apart. Makes a big difference if the saw comes back at you while spinning at 40 - 60 MPH.
Just because you have done it and not gotten hurt, does not mean that it is a good idea.
Not saying that these saws aren't light, and powerful, and capable of doing a lot of things. But the OP's challenge was to understand why their use is discouraged on the ground, while they are allowed for more specialized use up in the trees.
Philbert