Entry grades aren’t necessarily a measure of the quality of the degree. This is misunderstood by a lot of people.
Traditional universities set entry tariffs as high as they can - they are a measure of how popular the course is. Popular subjects have higher tariffs than less popular subjects, even if they are just as good. So do universities in popular cities. They set them high because it’s a lot easier to teach students who’ve done very well at A Level, they should all get at least a 2:1 and already have good study skills.
Widening participation universities are specifically there for ‘non traditional’ students, ie students who haven’t had a straightforward path or are from groups who don’t usually attend university. Perhaps they got made homeless during their exam years, or had a mental health crisis, or a baby. Maybe they joined the army at 16, or learned a trade, or went to work in a shop, and later want to study. Maybe they are a refugee. Maybe they spent their teenage years caring for a parent or younger siblings.
These institutions need lower tariffs because all of these circumstances can stop someone fulfilling their academic potential at 16-18. Low tariffs are there to give people an opportunity. Some will thrive on this opportunity and excel, and others will struggle and end up with a lower degree.
Your DS deserves a lot of credit for overcoming difficulties to get to Cambridge. But equally, the best students at widening participation universities deserve credit for also overcoming difficulties to also succeed academically. I welcome the fact that employers are recognising that there can be many routes to excellence.