Hey ProMaritime,
I appreciate you trying to help folks out. And, you are most certainly correct that a documented vessel shouldn't display state numbers but should do any required state paperwork, pay any necessary fees and taxes, and display a state sticker, as required. So, you've got the mechanics down pat -- and that is a lot better than some who occasionally post suggesting that state paperwork can or should be avoided for federally documented vessels!
But, what I think people are reacting to is a very narrow technical point. It is this bit: "registered (titled)".
I know it is a small point, but folks here tend to be sticklers. Call us pedantic, if you'd like. But, titling and registering aren't the same thing, and expressing an idea as "registered (titled)" suggests, at least to some, that they are.
One of my old law professors liked to say that "property isn't a thing, it is a bundle of rights and responsibilities". These rights and responsibilities are known as "title" of the property. One type of title, the "legal title", includes the rights and responsibilities of ownership, e.g. the ability to buy and sell. Another type of title, "equitable title" includes various rights of use and enjoyment retained from the legal title, e.g. access to the property. With vessels, unlike real property, the two types of title go are all part of legal title.
When buying or selling a house, ownership is conveyed by a document called a deed that transfers the title. This deed is then recorded in a record with the one proper custodian for the jurisdiction. This way, if someone wants to know who has title to a real property, they go to the one custodian, and look in the deed book.
With vessels and vehicles, there aren't really deeds, just title records or documents. These record who has title (legal and equitable, as one) to the property.
Since this type of record is important, there needs to be one custodian. In the case of vehicles, for example, they are titled by the state (except for federal vehicles, diplomatic vehicles, etc) and can only be titled in one state at a time. In the case vessels, the state is the custodian of record -- except for documented vessels, for which the federal government preempts state jurisdiction.
So, a USCG document, and a state title document or electronic record, are each documents describing who has the title of a vessel. Because there can only be one answer to this question, the title has to be recorded with the feds or the state, but not both. For certain vessels, one must record with the feds. For certain vessels, one must record with the state. For certain vessels one gets to pick. And, for certain vessels, title need not be recorded at all.
Registering is the process of entering information into an official record. It doesn't involve altering or creating that information. So, when one registers a car or vessel, one is telling the proper official about it, e.g. who owns it, their address, etc. But, one can't use the registration process to alter that information. I am who I am, I live where I live, and I own what I own. When I register a vehicle or vessel, I am simply entering whatever information is required (and/or optionally provided) by me into an official record. In many cases the information I enter won't be accepted without proof, e.g. I might not be able to register a vessel without a title, document, or proof of sale, etc.
Maintaining a record of title is critical to ensuring that the legal (and/or equitable) title holders of property can be credible determined.
Registration is critical to enabling other interests of the state, such as being able to contact an owner in the vent of emergency or liability, ensuring compliance with insurance laws, ensuring those registering are informed of critical local information, and/or collecting fees and other taxes.
As a non-vessel example, I bought my car in PA, and lived in CA for a couple of years. While in CA, I registered my car in CA -- but it remained titled in PA. Upon my return to PA a couple of years later, I reregistered it in PA, where it already happened to be titled.
As a vessel example, many "cruisers" have their vessels titled and registered in whatever area they call (or once called) their land home. And, while cruising as transients spending only brief periods in any state, that may be fine. But, if they hang out ion one state for too long (like Florida), they may need to register there, too. Unlike titling, there is no problem being registered in more than one state, so long as it is allowed (or required) by the local law.
So, I guess what I'm saying is that in normal conversations one might use words like register and title in an imprecise way, people here tend to be sticklers. They are different things. And, if one is casual about the distinction, well, that will often be observed.
Cheers!
-Greg