First, your parent comment misunderstood what the section they were critiquing is referring to. It's not about nullability (which is orthogonal) but about reference/value projections.

Now, as a member of the Java team (although I'm not directly involved in Valhalla), I'm obviously biased so let me just say that both designers and fans of programming language features would do well to remember two things:

1. Opinions about features are almost never universal, even among experts, and almost each of them is about a tradeoff where different people prefer different sides. It is rare that some scientific study settles the issue.

2. These preferences are often not evenly split. Even when both sides are equally confident that their preference is the right one, sometimes 80% or 90% of programmers share a preference. The people with the strongest opinions are more often than not in the minority, because most programmers don't think so much about the programming language (nor, I would say, should they).

All of the language differences between .NET and Java fall in this "non-consensus" zone, and at least in one area I was deeply involved with, virtual thread, I can say that we thought that whatever we do we mustn't do what .NET did and that what they chose didn't work out well for them at all.