It is de facto rationing, as the notion of one exercise per day is to stop everyone doing it all at once and overwhelming public spaces. Otherwise there’s no reason for it to be there.
I get that you’re unhappy having to rely on public transport, I sympathise to at least some extent. However people need to realise that there are people working quite simply to keep the most basic cogs of our society turning, and that *has* to take priority. There’s social media for conversing with friends and family, nowadays this can be done visually as well as audibly. For virtually all of the population this is the first time ever we’ve seen curtailments of our liberty, and there’s quite clearly good reasons for doing it. Many other countries are in the same boat, some more tightly locked down than us. It really isn’t *that* bad a deal being asked to stay at home as far as possible, compared to those who are playing Russian roulette with a relatively unknown virus simply to keep the processes going which ultimately do things like keep food on *your* table.
My point about rationing is that there's no control over when people take their daily exercise etc. It's hardly surprising if everyone turns up in the same place - people aren't all knowing and they don't know what everyone else is planning to do.
If the transition from lockdown to normality is going to take a long time, there is no reason why some controlled provision of public transport can't be made, for some limited leisure purposes to those with no alternative.