Ha ha ..... there's nowt wrong with curiosity and a thirst for knowledge, 7LM.
You'd be surprised what can actually pass an official 'pole test' ... some of them look like they're leaning quite badly to the naked eye, but they are still deemed to be safe. Conversely, a good number of years ago it was found that a certain batch of poles from a certain distributor were decaying inside far quicker than they should, as such, any poles thereafter with that particular manufacturer/species code were deemed un-climbable. To look at them they looked fine, which is why the official pole testers have a resistograph to check the density of the pole above ground and they use good old-fashioned digging techniques, to check a minor-arc proportion of the pole beneath ground.
As always though, H&S is the remit of the individual engineer and it could be a brand new pole placed in the ground the day before, if the engineer decides it isn't safe to climb that is his judgement call to make. Along with checking the pole markings and test-date cycle, they will perform their own 'hammer check' at various levels tapping firmly around the pole listening to any evidence of a change of pitch, it's hard to explain but you get experienced in what sounds ok and what doesn't. Add to that a probe test that also checks for damp/weak areas .... there's not much more they can do.
Can I also mention .... once you are up there, it looks a lot higher when you're looking down !! Plus, working in all weathers (apart from when there's lightning, or severe gales) adds another dimension to it. Up a stick is not ideal when it's cold, wet and windy.