The PRs they link mostly seem like noise? “Remove the d prefix from this number because the C++ standard doesn’t require it”. Yeah great.
Even if the changes aren't "meaningful" (which it seems like they are), they still have an impact in how it makes the contributor more comfortable with working on the project. No new contributor is going to start with making massive patches without starting out with some smaller things to get a feel for working with the project.
The d suffix makes it not compile under clang. The PRs seem like mostly small changes that are clear improvements.
The correct quote is: "Remove invalid 'd' suffix for double literals".
That's a pretty unfair characterisation of the commit in question: https://github.com/loongson/jdk/pull/125/commits/ee300a6ce73...
By my reading, it's not merely that the standard doesn't require the "d" suffix, it's that the standard doesn't allow the "d" suffix, and the code won't compile on anything but gcc.