I hope it does go ahead. Just two borders sounds like it should be reasonably manageable.
That's a good point about fairness. These things are never completely fair. Some people get injured and can't start, get hit by cars or bitten by dogs. Some can't get time off and some can't afford to take part, and so on. The Greek ferry being so long and late in the race already introduced a significant level of unfairness, and the test for Greece sounds like it just adds a bit more to it rather than creating a new problem where there wasn't a bit of a one already.
Probably a bit late now but, if they moved the finish to Sicily instead of Greece, it would get rid of the main issue, and be a lot more scenic too.
I think the NC4000 is more likely to go ahead as I get the feeling the organisers are desperate to make it happen and I suspect they won't have the same fairness concerns. They said a couple of weeks ago that they thought it was 99% likely to happen, which I thought was over-optimistic but indicative of intent. I put it at about 60% then.
If it does happen, with 9 border crossings, testing could become a real chore. And it's not clear (to me at least) that Brits are going to be able to go to Europe given the Indian variant issue currently blowing up in our faces. With 10 countries, it only takes one to say no for me to have to DNS.