Who said anything about the ideas in Shido Yoron as being standard practice for the Samurai?
The term "romantic" does not apply here. Saito Setsudo was a neo-confucian scholar with some very well formulated ideas. Quite a number of budoka still find his words inspiring.
If you do not agree with his ideas then do try to come up with some understandable counterarguments.
It is true that he had no battle experience - and how is this relevant? How much samurai battle experience do you have?
cited his ideas as a reference to the samurai and integrity. If you aren't of the opinion that they apply to the samurai then why quote them?
As I said, there's nothing wrong with those ideas, except I don't think they're a good example of samurai ethics (if there really was such a thing). And yes, I think some of his ideas are "romantice" when we're talking about their application to the samurai.
The thing about experience is the same thing that hampers the Hagakure as a realistic source of information about the samurai, that's all, no need to get excited.