I think the reservationist might have misunderstood your true intention and just quoted the standard company policy.

By "special requests", they probably meant early check-in, late check-out, disabled access, smoking room, etc...

If I were you, I would probably be taken aback, but not insulted. To be honest, who wouldn't want to have an upgrade? Put yourself in their shoes, when someone asked for an upgrade, what would you answer with? "Yes" - and it just set up bad precedents for the hotel, "No" - you'll feel how you feel now, "Maybe" (or equivalent fluff) - the hotel would probably get burnt. The customer would take that as a "yes" and demand an upgrade when check-in.

In short, don't worry about it. You're already going to a 5*, if you do get upgraded, it'll be a nice surprise.