if it was too risky to fall & I couldn't use a machine or a safe method I'd just leave it, after all they're still making them & not worth unnecessarily risking ones neck for .
I don't always have that choice. Much of what I cut is for firefighter safety. I don't care at all about saving out volume, or pleasing inspectors, or whatever. Sometimes I do have machinery to work ahead of or under, but not very often. I'll absolutely work under an excavator bucket if it's available but I don't carry one of those around in my back pocket. Usually it's just me and maybe a minimal crew. We make it work with what we've got because that's how things are. Always interested in how to work smarter.
Way too good of a chance of the top breaking out onto the machine. Even with all the forestry steel in the world protecting the cage it's not a great idea.
I watched the very thing happen last fall. Excavator operator was really jamming on a fir snag and the top accordioned back on him, well behind the tree's center of gravity. It hit hard enough to blast all of the glass out of the cab, not by breaking it but by pressurizing the cab and popping it all out of the seals. It was a hell of a hit, and while there were no injuries, the repairs were expensive.