I live in a state that had the first arborist laws in the USofA. Dating back to the 1920s. They were written into the state statutes under the Department of Consumer Protection. Included among those first laws was one prohibiting the spiking of live trees that were not going to be completely removed.
So, I was brought up that you never prune from spikes/spurs/gaffs. Guess I don't know any better.
I spent some time in Hawaii and California where I worked for companies that had contracts pruning street palm trees and I spiked every single one of them without a second thought. Shagging up an 80'+(25m+) Fan palm (Washingtonia filifera) ain't my idea of fun.
The ISA has issued guidelines for climbing palms that includes the installation of a climbing line over the top of a palm and ascending the rope to prune. Thank goodness I no longer have to worry about pruning those things. I could not imagine trusting the fronds to hold my rope in place, not to mention the time to place a rope in each tree and ascend the rope, much less working from a rope without a solid footing while trying to prune.
My, how times have changed.