There was no questioning or challenging by his Mum regarding him going to see a friend, considering he was shielding, I doubt it was the first time, IMO he was 'getting out' a little.
That's because the shielding advice then in force allowed daily outdoors exercise, and meeting one person to exercise with. Shielding, which was always advisory not compulsory, said you should try to stick with just the one other person, because even with social distancing, the more people you meet the greater your risk.
I suppose that as he was in a household with his mother, she should have been the one he exercised with, but that wasn't always going to be possible on a nursing shift pattern. And the consequences of stay-at-home nigh-on full isolation for months (as per March-June 2020) were considered too severe to be reimposed in later shielding.