My mistake - you said you were in a quiet residential area at 10pm. It’s probably best not to be in a park late at night, though.
If it's so absolutely fine to go for a socially distanced walk when you are self isolating, why isn't that in the guidelines?
Because they need a blunt tool to ensure maximum compliance. It’s got nothing to do with relative risk. It’s just that blanket rules are easier to enforce. It’s nothing to do with how the virus spreads, it’s to do with how humans behave.
It is not risky to go for a walk in the fresh air more than 2m away from someone you’ll pass briefly on a path, field or street in a low density population area.
It is a bit more risky in a high density population area.
If you are self isolating in a high density population area, and can’t get out without meeting people, stay in.
But people who can go out without meeting people aren’t some cavalier health-wreckers hell bent on infecting swathes of the population. That’s all.