So the TC is an interesting one. Not been in front of them myself (I drove PCV and work elsewhere in the industry now) But have had to study them and learn for CPC related reasons. One thing I would say off the beat, is TC driver hearings are generally open to the public, so if you want to go with your Son to watch what goes on, you can do (unless it states it's closed doors on the day) and there's the possibly that he may not be speaking to the actual TC, but a deputy on the day. Deputy's have the same power as the TC itself mind, so that point's rather moot.
The fact your son was driving and I assume, moving at the time will make this most likely lean towards as Newjudge said, towards the 4 week period. Length of service may come into account too with the TC potentially being more harsh based on less experience. One driver I spoke to who had been in front of the TC for mobile phone use (Looking at a bus stop, doors open handbrake on) was given a ban of 5 days instead of 4 weeks due to 27 years of service with no issues, this particular issue also being a report from the company (Most companies are obliged to inform the TC of these actions as part of operator license related duties)
Not really sure of anything else truth be told, I made an account just to respond to this post 
Firstly thank you for taking the time out to make an account just to respond to my post

The hearing is said to be on Microsoft Teams so not in person (not sure why) the vehicle was moving at 60mph and the offence was interacting (touching) a phone at 60mp, the looking down was what triggered the camera as it thought he was falling asleep, he also has in the past year collected 6 points on his normal drivers licence from speeding in his car on 2 separate occasions which as he had newly passed and gained a full driving licence within 2 years it was revoked, he then was not allowed to drive until he re-sat the theory and practical driving tests which he eventually did after some months and recently managed to find another job where he has been working for just a few weeks.
Yes very stupid things to do but sadly we can no longer give the kids a clip round the ear just hope that they have learnt from their mistakes and do better. He has lost a lot in terms of a well paid job and then his licence which has cost time and money so hopefully he has learnt enough lessons to not repeat them!
Thank you to all those that have given non-judgmental advice it is much appreciated.