The article you posted discusses the problem with neutering a dog too young. If you wait until they have reached sexual maturity, their hormones will help them grow properly. This is true.
However, in the long term the benefits of neutering greatly outweigh the risk. The risk of testicular cancer goes to near 0%, behavioral issues and aggression can often be addressed, etc. Unless you want to show or breed (breeding is a whole other debate) there is no need to have an intact male, IMO. Obviously, that is a matter of opinion.
As far as what you call "mastrubation"- it sounds like a boredom behavioral issue. I would up the amount of exercise he gets before and after work. Give him something to occupy his time, such as a kong filled with kibble or a bully stick. Something to occupy his time. It could also be a cleaning thing- some dogs like to stay clean. There doesn't seem to be anything sexual behavior wise in these actions. The physiological action occurs whether a dog is neutered or not- neutered dogs can even tie if they wanted to. It simply reduces that behavior by eliminating the hormones that encourage it. At what age was he neutered? This could be a behavior he had from before he was neutered.
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