Since you send all three at once, the agent is going to read them in whatever order she prefers, and this will almost always be letter, synopsis, chapter. It makes little sense to read them in any other order, so make it easy on her. Doing so is a pure waste of time and energy.
When you request all three, it's a pain in the butt having chapter first because it makes you think the writer might not have included the rest. Go with natural order, and with the way any sane agent, or editor, is going to read them.
Just because you probably read submissions one way doesn't mean that everyone else will.
How do you know for sure that the order agents prefer will "almost always be letter, synopsis, chapter"? Cite your sources, and in future make it clear that such things are your own opinions, and not some sort of legal requirement.
Submitting in ways that you don't like isn't wasting anyone's time or energy unless they're submitting to you--and bearing in mind that it doesn't seem that the OP is doing that, it's not necessarily an issue here.
Further, James, you've just implied that I am insane. Frankly I don't care what you think about my mental health, in relation to how I used to read submissions or anything else.
However, I do care that you think it's acceptable to suggest that people who don't do things the way you think is best are insane.
You're wrong, and you're rude, and you're this close to getting a time-out for it.