I know the job market has changed since I graduated - over 40 years ago, but I have never been held back by getting a Third! I was on track for. 2.1 at the start of my third year but just bombed my final exams and my dissertation was pretty poor as well, I have no idea what went wrong!
I already had a job offer before my degree result and the company did not ask me for my grade, just needed to know I had passed. My grade never came up in various internal promotions.
After a few years as a SAHM, I retrained as a teacher and even though I included my final grade on my university application form, they did not question it at the interview, they were more interested in any experience I had of volunteering in schools and the subjects I had taken at University - had to be one that linked to the National Curriculum.
I ended up as Assistant Principal and SENCO of a large Secondary school before retiring a few years ago. I was a bit ashamed of admitting I got a Third but it rarely came up and I was not held back.
Hopefully with a 2.2 your son will succeed in his chosen career, my son, age 36, got a 2.2 and now works in digital marketing earning over £80k a year so his degree certainly has not held him back either. He has dyspraxia and was given support for that at University which helped him a lot. He was more hindered by his painful shyness which meant he struggled in interviews but once he moved up the ladder a bit, he was headhunted by agencies for more recent jobs.