Uh, no. I'd give the agent EXACTLY what s/he asks for, neither more nor less. I'd not assume s/he wants a query (or anything else) if s/he does not ask for it. They get a flood of stuff every day & I don't want to waste their time.
I don't see what the benefit of that approach is. Query letters, in the U.S., are ubiquitous. If done well, they're short, they're clear, they do a particular job.
An agent or agency requesting a synopsis and chapters, likely in addition, will get tons of queries + that. Opening a synopsis and reading it instead of a query likely isn't going to give the same experience of the material. Why risk someone thinking you don't know how to query just to show you followed exact instructions that likely took something for granted, when, if that was meant, they'll get a ton of queries with the stuff anyway?
If someone doesn't want queries, I'd think they'd be specific to that end.
