In a way it's worse because at least with int you're not really expecting to run the same binary on architectures with different int lengths, and also for several decades there have only been two realistic options (32 or 64), which makes it easy to deal with.

With RVV (and SVE I assume) there are a wider range of realistic options - at least 128, 256 and 512. The RVV spec allows up to 65536! Also it's totally reasonable to want a single binary to work with all of them so then you're into compiling parts of your code multiple times with runtime dispatch which is a right pain.

I haven't looked into how Highway does it but I don't really know you you write length-agnostic code in high level languages. It's easy in assembly, but it sucks if you have to do it in assembly.