Saying you “agree” with one shitah of rishonim is arrogant, presumptuous, and belittling of all the other opinions. It’s saying that you’re entitled to decide who among them was more correct. That’s when it’s a typical machlokes.
Here it’s a daas yochid; effectively saying that the vast majority of ashkenaz rishonim and achronim are wrong and that their holy words are chas veshalom “shtus”