How do HTTP/2 and HTTP/3 change things? (Sonnet 4.6 and ChatGPT [idk default free] told me they don't. Gemini 3 Fast gave me a long essay on how they technically do.)
Mostly it seems like it's other things--CNAME flattening and whatnot--that make it unnecessary.
But it's been unnecessary since long before HTTP/2, and we do it for semantic or historical reasons. I don't think anyone is including www because they think it's technically necessary.
If you want me to change the way I do things, make your case and support your claims! If the entire point here is "you don't need to include www", well, yeah, duh, we've all visited apex domains. We know it's a perfectly valid option.
It also missed out on making an obvious reference that would also add a reason for its recommendation: "Drop the www. It's cleaner."