Kicking relatively soft baby trees make for cool YouTube highlights but not practical for regular training.
Never once have I seen fighters hitting their shins with sticks or kicking poles. If you have a nation of fighters training, how many acres of banana tree plantations would sacrifice their crop for boxers? Probably none.
So to answer your question. Shins are harder than you think. Rarely do shins break in a fight. If a shin breaks while it is blocked it’s almost always on the lower third part of the shin. The top third of your shin nearest to the knee is the strongest part of the shin. I’ve not heard of a break on that portion. Which is the ideal part of the shin we use to strike and block.
All people have nerves that are sensitive to impact on the shin. Think about a time you bumped into a table corner or bicycle pedals slamming back on your shins. Painful. Muay Thai fighters learn to overcome this pain by kicking pads, bags, sparring, running, strength & conditioning, etc. Normal training for a fight is very tough and if you were to fracture your shins in training you wouldn’t be able to train to your max potential day in and day out. Twice a day. All this training makes you mentally tougher and resistant to adversity. The repeated contact of your shins through normal training is enough dull some of the pain over time. Lots of time. Running and strength training increases bone density and general resilience of tendons and muscles.
Listen to your qualified trainer and put in a ton of hard work and then one day you can kick and block kicks with a lower likelihood of breaks and pain.
Last note. It freaking hurts to have your kick blocked or blocking kicks repeatedly sometimes. Even my personal muay Thai heroes experience pain and damage to their shins from time to time.