Granted, others mentioned prosecution, but you did explicitly state "why else would the head call him in if it wasn't abuse". But it's not abuse, not even remotely close. It's not even a grey area. It wasn't necessarily a good idea, or perhaps even necessary, but to call it abuse is frankly, utterly Batshit.
I know you work in a school, and have done your course, as you've told us, but it's laughable that you think you can detect who hasn't had safeguarding training based on who agrees or disagrees with you. I can guarantee I have had more safeguarding training and direct experience with genuine abuse and safeguarding cases than you have, and I still think you're wrong.
And all your comments about being fired if you were to hug a distressed child are either hyperbole or reflective of a school/DSL writing policies to cover their own back rather than prioritising child safety. The primary aim of safeguarding is to protect children from harm, including psychological and emotional harm. Denying a distressed reception/KS1 child from a reassuring arm around the shoulder/side hug if that is their preference is going to do them far more harm than a measured, considered approach to physical contact, and such policy would only be written in such a way if the schools priority was protecting themselves. It's perfectly possible to write a "safe touch" policy, and indeed most schools I have come across have done so. Obviously physical comfort becomes less as they get older, as part of school education is learning what is and isn't appropriate in professional settings as they prepare to enter the working world, but to suggest once they cross the threshold from nursery into school, or reach compulsory school age that it's automatically unacceptable to touch them discredits any legitimate points you may have raised, tbh 🤷🏼♀️