Tree surgeons are very experienced in using chainsaws and have all of the correct (very expensive) safety wear.
Cutting logs that are firmly clamped in place whilst standing on the ground is dangerous enough with a chainsaw. Using one to cut a trunk which is waving about whilst on a ladder with the chainsaw at waist height is beyond ridiculous for a new chainsaw user with none of the safety gear.
I have used a chainsaw for many years in a DIY capacity and I would still not use one to cut down a standing tree trunk.
